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CCEaUGHT DEMSm 



OUR WORLD 



Our World 



A Sketch of Origins 

ACCORDING TO SCIENCE 
BY 

CHARLES HARVEY PECK 

Author of "The Jacksonian Epoch" 




NEW YORK 
THE FRANKLAYE PRESS 

MCMXXI 



£ 



Copyright, 1921, by 
Charles Harvey Peck 



<9* 



All rights reserved 



ICI.A630213 



NOV 12 1921 

Printed in the United States of America 



Malvolio : I am not mad, Sir Topas : I say to you, 
this house is dark. 

Clown: Madman, thou errest: I say, there is no 
darkness but ignorance ; in which thou art more 
puzzled than the Egyptians in their fog. 

—Twelfth Night, Act iv, Scene ii. 



PREFACE 

SOUND ideas relating to the public welfare 
are not effective until so generally shared as 
to guide public opinion. The essentials of physical 
science are the basis of all sound thinking. The 
more thoroughly and generally they are under- 
stood, therefore, the better for social, political 
and economic conditions. The sole purpose of 
this book is to present in as brief compass and 
plain terms as practicable the principal data of 
general science as now accepted, without ex- 
ploiting special theories. If evolution appears to 
be the key to explanation of our world in all its 
phases it is because the evidence now admits of 
no other. 

The chief difficulty in preparing such a book 
is the choice of materials from a vast and various 
mass from many sources. Yet this difficulty is 
somewhat lessened by the consideration that most 
of the details of science have been developed in 
the search for principles and in the application 
of those principles to practical uses. The ar- 
rangement follows the natural sequence, except 
that, for clearness, some general causes are stated 
in connection with specific phenomena; for the 
main divisions of science overlap and are gov- 
erned alike by the laws of matter. 

C H. P. 



CONTENTS 

Chapter Page 

I Cosmic Phases . . . . 1 1 

II In the Beginning 36 

III The Geologic Record 67 

IV Ways and Means 96 

V Life 123 

VI A Prehistoric Pedigree 155 

VII Mind and the Aggregate 185 

Notes 213 



OUR WORLD 



CHAPTER I 
COSMIC PHASES 

THE SPECTRUM 

THE spectroscope, devised by Kirchhoff and Bunsen in 
1859, shows the elements of any object that emits 
light, whether a distant orb or a filmy nebula. It has solved 
the mystery of certain of the variable stars, made the sun 
a field of intimate research, and shown the direction in 
which the solar system is traveling. These and similar 
results have revolutionized astronomy and projected the 
theory of evolution through the vast of starlit space. The 
nature and functions of this instrument must be understood 
before the facts it has demonstrated can be fully appraised. 

Light is a result of motion of or within the atoms of 
the matter affected and communicated by the ether sup- 
posed to pervade all matter and all known space. The 
presence of this ether cannot be proven by any method yet 
known. It exists in theory to account for the waves of 
energy — heat, light, and electricity — which are known and 
determined with extreme accuracy. 

For many years dark lines across the various colors of 
the solar spectrum had attracted attention. They are called 
the Fraunhofer lines, from the name of the investigator 
who first made them the subject of serious investigation; 
but it was not until after the spectroscope came into use 
and the wave theory of light was generally accepted that 
the results were explained and applied to the solution of 
many problems of astro-physics. Spectrum analysis has 
thus become a leading factor in the modern science of 
astronomy and a powerful aid in physics and chemistry. 

11 



12 OUR WORLD 

It has led td several improvements in the instrument which 
have added greatly to its value in the many uses to which 
it is put. The most important of these is in substituting a 
so-called grating in lieu of prisms. This grating is a plate 
of glass or speculum metal ruled with accurately spaced 
and parallel lines, in some cases with 60,000 or more to 
the inch — in itself an extraordinary mechanical achieve- 
ment. The main purpose of these appliances is to lengthen 
the spectrum by diffraction in order to show all the lines, 
which number many thousands, but with as little loss of 
brilliancy as possible, since the difficulties of observation 
increase with the distance from the source of the light. 
The grating also permits an accurate count of the fre- 
quency of the waves — the number per second, which is 
of vital moment in many investigations ; and considering the 
fact that the sensation of sight is produced by waves ranging 
from 400 million million to 800 million million, in round 
numbers, per second, the measurement and analysis of these 
waves rank among the greatest technical attainments of 
science. 

The rays are admitted through a minute slit, say one- 
tenth of an inch long and one-thousandth of an inch wide, 
to pass through a lens making them parallel; thence to a 
series of prisms, an echelon of thin glass plates, or a grating, 
which transmits or reflects them through another lens by 
which they are focused a short distance in front of the eye 
or a photographic plate for permanent record and compari- 
son with the results of laboratory investigation, so far as 
that is possible. The prisms, owing to lesser loss of light, 
are most used in astronomical work, in connection of course 
with the telescope. 

Every element, when heated to the point of incandes- 
cence can thus be identified, under suitable conditions, as 
infallibly as a person by his fingerprints, for the spectrum 
of one element is never duplicated by that of another. When, 
therefore, it is found that a given element — iron or hydro- 
gen, for example — shows certain characteristics by exam- 



COSMIC PHASES 13 

ination in the laboratory, its presence in a distant star or 
nebula will likewise be indicated. Investigations so con- 
ducted have established several results of decisive import 
in studying the constitution, evolution and motion of the 
stars and other astronomic objects. 

The spectrum of an incandescent solid body, a liquid or 
a condensed gas is continuous, that is to say, the normal 
colors are not crossed by lines of any kind. The spec- 
trum of an incandescent gas or vapor consists of bright 
lines arranged according to the different elements, or bright 
lines upon a faint continuous spectrum. If the light is 
from a source that would otherwise yield a continuous spec- 
trum, but passing through gases or vapors less heated, dark 
lines are produced by absorption. When such a body is 
moving toward the earth or the earth toward it, the lines 
shift slightly toward the violet; and when the body is re- 
ceding from the earth or the earth from it, the shift is 
toward the red. The rate of this change, as found by com- 
parison with a similaf spectrum of a stationary light, affords 
data from which the speed may be calculated. By this 
method the velocity with which stars and comets are moving, 
the orbits of the variable stars, the path of the solar system 
and many other motions involved in the problems of celes- 
tial mechanics are determined. And be it understood that 
these conclusions are not theories, but facts as provable as 
any in physical science. They are the effects of the laws 
of light, which inevitably follow from the nature of light 
itself. 

Light radiates through free space — as from a star to the 
earth at the rate of 299,800 kilometers (186,330 miles) per 
second, the velocity being calculated with a precision correct 
within 30 kilometers. This amounts to about 6 million 
million miles per year. The stars are all at such great dis- 
tances from us that the unit of measurement is called a 
"light-year," the distance that light travels in a year. The 
nearest lucid star, Alpha Centauri, 1 in the southern hemi- 
sphere, is about 4^ light-years from the sun; the next 



14 OUR WORLD 

nearest, a catalogue star (21,185 Lalande), in a different 
direction, is 7 ; and Sirius, the brightest of all the stars, in 
a yet different direction, is 9. The average distance between 
neighboring stars, so far as their distances have been cal- 
culated, is from 6 to 8 light-years ; and probably the remote 
stars are similarly spaced, except where there are groups 
or clusters of stars comprising systems. This average, of 
course, is only a rude generalization, for the variations are 
many and enormous. 

To ascertain the distance of a star is one of the most 
delicate and difficult measurements in astronomy. The 
method thus far employed is that of triangulation, the 
same as that used by surveyors in topographical work. The 
conditions create the difficulty. The angles can be deter- 
mined only by the parallax — the apparent change in the 
position of a star produced by the change in the position 
of the earth in its orbit around the sun. The base line of 
this measurement is the diameter of the orbit, about 186 
million miles. Yet this is too short to afford a basis for 
calculating the distance of only a very small proportion of 
the stars. Even some of the brighter ones are so far away 
that an appreciable angle cannot be defined. Recently such 
progress has been made in estimating stellar distances by 
means of the characteristics and degrees of light from 
variable stars in clusters so far distant as to show no paral- 
lax that there is some prospect of perfecting methods that 
will also determine the distances and dimensions of stars 
that are not variable. These methods are a development of 
spectrum analysis. 

A FINITE UNIVERSE 

The total number of stars visible through the greatest 
telescopes is somewhat less than 200 million, though the 
number that can be photographed is much greater. It is 
mathematically certain that if the brilliant stars were infinite 
in number, and light suffers absolutely no diminution in 
passing through space, the entire sky would be suffused 



COSMIC PHASES IS 

with a glow. There is no evidence as yet that light is so 
diminished; and there are substantial reasons for thinking 
that the number of stars is limited. Astronomers are almost 
unanimously of opinion that the stellar system which con- 
stitutes our universe is not infinite, but is limited in all 
directions. The evidence indicates a spheroid formation, 
much flattened, the northern hemisphere of which i§ not 
coincident with the vista presented by the skies of the earth's 
northern hemisphere, the plane of the equator forming an 
angle of about 62 degrees with the plane of the Milky Way. 

This conception is founded upon the most thorough obser- 
vations possible to make. The total number of stars shown 
by photographs of all the stellar regions reveals a pro- 
gressive decrease away from the Galaxy, while through the 
Galaxy the distance is so great that the stars more remote 
cannot be resolved by the most efficient instruments; yet 
the spectroscope shows unerringly that the glow in the out- 
lying and impenetrable regions is light from condensed 
bodies. In other words, if the average number of stars per 
unit of space is the same in the Galaxy as it is toward the 
poles, the effect we behold would be produced by the greater 
distance through it — the greater extension of the equatorial 
plane of the spheroid. 

No other theory accounts for the phenomena; and it is 
aided by the present position of the solar system. The fact 
has been established that the sun and its retinue are moving 
in the general direction of the constellation of Lyra, near 
the present position of the magnificent Vega, a star of the 
northern hemisphere. The speed of this motion is about 19 
kilometers per second. A simple calculation will therefore 
show that the early history of the earth, even of the human 
race, was passed in a vastly different region of the universe 
from that through which it is now voyaging. 

Yet the velocity of the sun is very much less than that 
of most of the stars, so far as their motion is known. The 
average speed has been estimated at 26 kilometers per sec- 
ond ; but such an average has small significance because of 



16 OUR WORLD 

the enormous variations from it. Some of the stars are 
moving at such a rapid rate as to forbid any idea of relation, 
except in those cases where similarity of speed and direction 
among a group of neighboring stars indicates a separate 
system. The beautiful Arcturus was long supposed to have 
the greatest velocity of any star — between 200 and 300 miles 
per second. Even in ancient times its change of position 
was noted by the diligent students of the heavens. Modern 
astronomy, however, has found that this speed is exceeded 
by several other stars of telescopic order. It has often been 
remarked, as illustrating the vastness of stellar distances, 
that notwithstanding the movement of all the stars if the 
astrologers of antiquity could now survey them they would 
detect no considerable changes in the constellations with 
which they were so familiar. 

In studying the possibilities of the celestial mechanism, 
the diversity of direction in stellar motion is a fact of much 
importance. Efforts have been made to find evidence that 
the movements of the stars are governed by some sort of 
universal concert; but they have thus far been unavailing 
on anything like a general scale. Two great streams in 
opposite directions, but parallel with the galactic plane and 
perhaps other streams, are thought by some observers to be 
shown by transverse motions ; but these conclusions embrace 
but a small proportion of all the stars. In any event, there 
remains a diversity of movements that cannot now be 
brought into any semblance of system or coordination. 

It would seem remarkable if there were no star streams. 
If the spheroid conception of the universe be true, what- 
ever may be irregularities of the exterior, there must be a 
cause or combination of causes, and the only causes now 
conceivable are gravitation and momentum. If the solar 
system be near or within easy view of the central region, 
the conclusion is obvious that the planetary type of motion 
does not propel the stars around a central body. In fact 
neither the sun nor any of the stars, the proper motion of 
which has been determined, reveals an orbit. Measurements 



COSMIC PHASES 17 

have not been conducted long enough; and it may require 
many centuries of observation before sufficient data can 
be accumulated to determine with any assurance whether 
stellar movements have an orbital character. 

There are, of course, many stars very much larger than 
the sun; but this difference is more of extension than of 
mass. The largest known stars are greater than the sun, 
in most cases, mainly because they are in a more diffused 
or gaseous condition, which contracts with age. Again as- 
suming our universe to be finite in extent, it may be readily 
imagined that the ether or other medium of radiation does 
not extend indefinitely beyond the outer stars ; hence there 
would be no ultimate loss of potential energy by dissipation 
into space. Inasmuch as the universe shows no signs of 
condensation after the lapse of inconceivable time, the prob- 
lem is narrowed to the principle of perpetual motion, which 
appears to actuate the material universe in the atom and 
at large ; and this problem may lie in the realm of the un- 
knowable. 

EVOLUTION OF STARS 

Armed with the spectroscope, astronomers were not slow 
to apply the theory of evolution to the stars. The evidence 
was so suggestive that the principle gained general recogni- 
tion. The universality of the laws of gravitation and radia- 
tion was supplemented by the discovery that the elements 
and properties of matter are the same wherever matter 
exists in the universe. These elements do not always exist 
in the same combinations, and it is not apparent that all 
of them are in every astronomic body. Thus certain ele- 
ments exist on the earth that are not known to be in the 
sun; and certain other elements are in some of the stars 
and nebulae that are not known to be in others. These 
facts are shown by the spectroscope ; indeed, there are many 
lines in some of the spectra that are not yet identified. 
These discrepancies are the subject of unremitting research 
and will doubtless eventually be accounted for. Without 



18 OUR WORLD 

pursuing this highly technical branch of science further, it 
suffices to say that the unusual and unknown elements 
form but a small proportion of the masses of matter scat- 
tered through the cosmos ; hence the assumption is entirely 
safe that the material universe is as homogeneous in its 
constituents as it is in its laws. This leads to the conclusion 
that the evolutionary processes of the stars are general, 
the results varying with the conditions. If, therefore, it 
can be determined what the several stages are, we may 
form a definite conception as to the origin of the solar 
system and of the earth itself. This has naturally become 
the paramount object of astronomical theory and research. 
That great progress has been made will be manifest by 
an untechnical recital of the leading facts which the tele- 
scope, the spectroscope and the camera have demonstrated. 
Any theory of stellar evolution is confronted at the outset 
with two formidable obstacles : the remoteness of the stars 
and the duration of time required for their successive periods 
of development. As the former has, in some degree, been 
surmounted by optical aid, so has the latter by the great 
number of stellar objects representing all the stages through 
which matter passes in being organized into stars and sys- 
tems, excepting the lesser features of planetary character, 
which probably exist in immense numbers, though invisible. 
Within the entire range of the intellectual faculties there 
is nothing approaching in sublimity the ideas evoked by this 
wondrous panorama, viewed as stages in the evolution of 
worlds. 

MULTIPLE STARS 

There are now known about 150 stars that are variable 
in brightness because of partial eclipse. In each case an 
obscure companion passes at regular intervals between the 
star and the line of sight. Of this class, Algol is usually 
taken as the type of a very significant phenomenon; hence 
some details concerning it will be illustrative. It has long 
been known as the demon star (that being its name in 



COSMIC PHASES 19 

Arabic), owing to its plainly visible wink, during which it 
changes from about the second to nearly the fourth magni- 
tude for a short time during every period of 2 days, 20 
hours, 48 minutes and 55 seconds. The star is somewhat 
more than 1,000,000 miles in diameter, and the companion 
about 800,000, a little less than that of the sun. The dis- 
tance between the two is somewhat more than 3,000,000 
miles, and their combined mass about two-thirds that of 
the sun. At long intervals occur slight irregularities in the 
rhythm of the variations, which have been ascribed either 
to the revolution of both bodies around a third invisible 
one, or, more probably, to perturbations caused by the attrac- 
tion of other members of an invisible system. 

In all instances of the Algol type the essential features 
are similar — a light and a dark or less brilliant body pro- 
ducing a periodical eclipse because the plane of the mutual 
revolution happens to lie in the line of sight. As this phe- 
nomenon is possible only because of the accident of position 
and the fact that the two bodies are relatively near together, 
there are undoubtedly great numbers of unknown binaries 
of the same type which cannot be detected. Moreover, the 
presumption arises that the visible stars form but a com- 
paratively small part of the entire number of stellar bodies 
comprising the universe. There is, of course, no way to 
reach even an approximately reliable estimate as to the pro- 
portion; yet some eminent authorities have expressed the 
opinion, based upon the motion of the visible stars impelled 
by universal gravitation, that they number at least four or 
five dark bodies to every one that is luminous. The pro- 
portion, however, is not very important to the general theory 
of evolution. It is enough to know that dark bodies are 
numerous and that in earlier stages they were incandescent, 
having lost their light through radiation ; and unless the uni- 
verse is slowly running down — a rather irrational thought, 
in view of the great number of nascent stars — they are 
awaiting the action of conditions and forces that may sooner 
or later revive their dormant energies. 



20 OUR WORLD 

Another type of binaries which perfectly illustrates a stage 
through which Algol's companion has passed is the star 
known as Beta Lyrse, in the same constellation as Vega and 
at intervals nearly as brilliant. This also is composed of 
two stars revolving around a common center of gravity in 
an orbit directly in the plane of vision. Both are still in 
a highly gaseous state, the mean density of the system being 
a little less than that of our atmosphere. The larger of 
the two is about twice the mass of the smaller, and, as 
might be expected, is only about one-half as bright, doubtless 
owing to the greater rapidity that marks the evolution of 
the smaller bodies ; yet the mass of the main star is nearly 
ten times that of the sun. The centers of the two bodies 
are about 30,000,000 miles apart. As these figures are based 
solely on results of the spectroscope, they are only approxi- 
mate, but no doubt are accurate enough to afford a fair 
idea of the material facts. Both bodies being bright, they 
are more brilliant when seen side by side than when one is 
behind the other, and therefore present the appearance of 
a variable star at regular intervals. The number of binaries 
of this type is very large. 

A still earlier phase of stellar development is clearly shown 
by a large number of stars of the U Pegasi type. Here are 
two bright gaseous bodies either in contact or nearly so. 
This condition is more difficult to observe, particularly in 
remote stars, because when the lines of the spectra are not 
sharply defined precise calculations cannot be made; yet it 
may be a common process by which binaries are formed, re- 
sulting from the rapid rotation of a huge body in a rarified 
state. It first becomes a pear-shaped mass, which then divides 
into two separate bodies of unequal size. These tend 
through tidal movements and condensation to draw farther 
apart until a stable distance is reached according to the 
law of gravitation. And here would seem to be the main- 
spring of the mechanism that prevents the consolidation of 
nebulous matter beyond the limits fixed by its physical con- 
stitution. Evidently, matter can combine only so long as 



COSMIC PHASES 21 

the power of gravitation is greater than the momentum of 
revolution — centrifugal force; and that gaseous bodies re- 
volve at higher rates of speed after consolidation sets in, 
and because of it, is^apparent from the fact that all the stars, 
like the sun, in their gaseous stages are spheroids through 
physical necessity. If two or more bodies collide the heat 
generated resolves their masses into a gaseous condition in 
which the former processes are renewed. This may be so 
or not ; but the hypothesis is as reasonable as any that can 
be formulated in the absence of positive knowledge. "The 
system," says Campbell, "would not run down until all the 
kinetic energy had been converted into heat, and all the heat 
generated had been dissipated. This would not occur until 
all material in the universe had been combined into one body, 
or into two bodies in mutual revolution. However, if there 
are those who say that the universe in action is eternal, 
through the operation of compensating principles as yet 
undiscovered, no man of science is at present equipped to 
prove the contrary." 

These three types of binary stars, variable because of the 
character and motion of their components, exist in all man- 
ner of gradation, as might be supposed from their number 
and apparent differences in age and composition. Besides 
these types, tens of thousands of other double stars are dis- 
closed by the telescope. With these, the orbits are not in 
line of sight, hence they appear merely as double, where 
both are luminous. In many cases one or both of the 
components are also double. In addition to the vast number 
of stars known to be binaries, it is thought by competent 
authorities that nearly one-half of all the other stars that 
appear single are really double. In any event, the phenom- 
enon is so common in all quarters of the universe that it 
must indicate the normal course of evolution in conditions 
that are very general. 

That such conditions have existed on an immense scale 
in diverse regions is shown by the fact that, besides the 
pairs of stars, there are very numerous systems composed of 



22 OUR WORLD 

from three stars to clusters containing many thousands. For 
example, Mizar and Polaris are triple. Castor and many 
others are quadruple. Theta Orionis is one of a system of 
six, and Epsilon Lyrae, of seven. The Pleiades, whose six 
most visible stars are known to every one who has the 
slightest acquaintance with the northern skies, have also 
several thousand telescopic members all moving together 
in the same general direction accompanied by a more or 
less nebular environment visible by reflection and possibly 
in the way of being gradually absorbed, or, as some observers 
maintain, the product of stellar dissolution. 

These systems exist in every variety ; stars of every order 
of brightness are combined in every way ; and in many clus- 
ters the proportion of variable stars is large. Even the 
larger clusters are varied in form and constitution. Some 
are small and irregular both in outline and in the distribu- 
tion of the stars, like Pleiades, while others are enormous, 
like the Magellanic clouds in the southern skies, resembling 
in their general appearance the character of the Milky Way. 
Other clusters, to the number of several scores, are globular, 
and their components are arranged with considerable regu- 
larity, like the aggregation in Hercules, which to the naked 
eye is a luminous cloud, but is resolved by the telescope into 
thousands of stars, each one a sun. How all these clusters 
assumed and maintain their present character are secrets 
for the future to solve. 

Recent investigation of star clusters, however, has already 
greatly advanced the state of knowledge concerning them. 
One important result has been to confirm the probability 
that all the known clusters belong to the sidereal system of 
which the Milky Way is the principal evidence. But this 
result has also greatly enlarged prior conceptions of the 
size of that system. The dimensions of the greater clusters 
are so vast that the stars composing them are scarcely 
nearer to one another than those of our own region of the 
skies. The relatively slight attraction of bodies so far sepa- 
rated is evidently balanced by their motion, and this, in 



COSMIC PHASES 23 

general, prevents any group or cluster from coalescing 
through gravitation. 

STAGES OF STELLAR EVOLUTION 

Important as are the results so far attained through the 
study of the variable stars, similar investigations of the 
physical nature and stages of stellar evolution have been 
even more fruitful of definite knowledge. So many stars 
of every variety are within reach of optical examination 
that the study has been conducted by many astronomers 
and physicists with unflagging zeal and brilliant achieve- 
ment. These cosmic phases are rapidly assuming the aspect 
of an exact science ; but they are so diversified, so complex 
and so technical that in a general sketch only the more 
salient features may be presented. 

The red stars are at the extremes of the scale of classi- 
fication. They are the youngest or the oldest, not neces- 
sarily in time, but in the stages through which they have 
passed; for obviously the stages of evolution of a small 
star would be shorter than those of a large one — the heat 
would sooner be dissipated. Yet the red stars, to be visible 
for the immense distance their light must travel, must have 
gained or retained a considerable degree of brightness. If 
a star is not in a brighter stage than Jupiter, of the solar 
system, it is totally invisible ; not even the dark companions 
of the double stars can be seen by reflected light. At best, 
therefore, in studying the evolution of stars, direct knowl- 
edge cannot extend much beyond the point w r here consoli- 
dation has reached the state of incandescent gas. But for- 
tunately from this point the members of our own system 
unquestionably illustrate aptly enough the later phases of 
all stars that have lapsed into invisibility. 

In recent years the spectroscopic study of the stars has 
developed a generally recognized gradation into- classes 
ranging from blue to dark red. This is the usual way of 
arranging them in the order of the successive phases through 



24 OUR WORLD 

which they pass from youth to old age. This classifica- 
tion, however, is not sharply defined, since the various types 
shade insensibly into one another. Thus between the dark 
red and the reddish yellow and the yellow and the light 
blue stars the tints are very numerous. The spectra of 
the great majority of stars are continuous, except for dark 
or absorption lines, which increase steadily from a few for 
the blue stars to many for the red, of the old or dwarf 
stars. In their early stages, whatever the degree of bright- 
ness, the stars are so diffuse and therefore of so much 
greater size that they are called "giants." This condition 
distinguishes them from the older "dwarfs" which have 
shrunk through condensation. It is supposed that the length 
of time required for a star to gain its maximum brightness 
is much less than for it to expire. This subject is yet a 
difficult problem, but it is of profound interest, as the exist- 
ence of life on the earth depends upon the continuation 
of the sun's heat at not very much less than the present 
degree. 

The changes in the spectra of the stars as they pass 
through successive stages suggests the inquiry, Why do not 
the elements shown in the older stars appear also in the 
younger if they are present, as they must be potentially at 
least? The answer invades the most obscure province of 
physical chemistry. "The conditions," says Campbell, "in 
the nebulae and in the youngest stars are such that only the 
simplest elements like hydrogen and helium, and in the 
nebulae nebulium, which we think are nearest to the ele- 
mental state of matter, seem to be able to form or exist 
in them; and the temperature must lower, or other con- 
ditions change to the conditions existing in the older stars, 
before what we may call the more complicated elements 
can construct themselves out of the more elemental forms 
of matter. The oxides of titanium and of carbon found in 
the red stars, where the surface temperatures must be rela- 
tively low, would dissociate themselves into more elemental 
components and lose their identity if the temperature and 



COSMIC PHASES 25 

other conditions were changed back to those of the early 
helium stars. There is no evidence, to the best of my 
knowledge, that the elements known on our earth are not 
essentially universal in distribution, either in the form which 
the elements have in the earth, or dissociated into simpler 
forms whenever the temperatures or other conditions make 
dissociations possible or unavoidable." 

The sun may be taken as the best standard for comparison. 
It is a yellow star — in middle-age, so to speak. Its average 
density is one and one-half times that of water. Its equa- 
torial diameter (865,000 miles) is much less than it was at 
the time its planetary system originated, as shown by the 
fact that all the stars of the early types average many times 
larger and are correspondingly less dense. By reason of 
gravitational pressure, the core of a star is necessarily much 
more compact than the outer parts and also heated to a 
much higher degree, which serves during the youth of the 
star to more than compensate the exterior for its loss by 
radiation. When the maximum external heat has passed 
and begins to fall, the bright lines that cross the spectrum 
of a star of an early type — showing an extremely high tem- 
perature of the gaseous envelope, the outer part of which 
is usually hydrogen — give way to the dark lines, which in- 
crease during the time that the star is bright enough to yield 
a spectrum. As the atmosphere becomes cooler and denser 
the complex spectra of the metallic oxides make their appear- 
ance. And this is true notwithstanding the fact that the inter- 
nal temperature of the star must still be very high. The 
convection currents from within outward are less free as 
the body contracts. And this condition is the probable 
explanation of a type of variable stars in which the changes 
in brightness are not due to the causes already stated. These 
changes, while more or less rhythmic, are not strictly reg- 
ular, and are therefore supposed to be caused by physical 
convulsions (radiation pressure) somewhat akin to those 
manifested by the so-called sun-spots, but on a much more 
extensive scale. 



26 OUR WORLD 

Another general fact bears strongly on the theory of stellar 
evolution. The average velocity of the forward movement 
of stars in the early (helium) stage is much less than that 
of the older (hydrogen and solar) stars; and the speed of 
the latter is less than that of the later types. Moreover, 
the components of the early double stars are so close to- 
gether that they cannot be visually separated, while those 
of the later types are more and more widely asunder. The 
mutual revolution of the early pairs may occur within a 
few hours ; with the later types, it often becomes hundreds 
of years. These movements are unquestionably the normal 
results of gravitation. Likewise newly formed stars do not 
elongate and divide when their size, composition and mode 
of formation do not compel the paired type of development. 
Assuredly the same general laws underlie both classes of 
phenomena ; and the same general laws undoubtedly compel 
the aggregation of clusters on one hand and the dissociation 
of pairs and groups on the other, when the proximity of 
other bodies or systems exert their gravitational force. If 
science has established one conclusion more absolute than 
another it is that no phenomenon is haphazard, but is pro- 
duced by a cause or combination of causes obedient to the 
fixed laws that govern matter. Evolution is the natural 
sequence of cause and effect through the operation of the 
laws of matter upon the conditions present. 

It must not be understood that the opinion of astronomers 
is unanimous that the course of stellar evolution here out- 
lined is proven beyond doubt; but it is clear to anyone 
familiar with the trend of astronomic theory that the opinion 
of the great majority of those most competent to judge is 
that the facts, so far as known, point to evolution in the 
reversing order of color and brilliance. Nor is it to be 
understood that there are no apparent exceptions to this 
order. There are phenomena which do not readily fall into 
classification and which science is not yet able to explain. 
But when we consider the shortness of the time during 
which current conceptions of matter and motion have guided 



COSMIC PHASES 27 

the study of astronomy, it is not strange that the manifold 
aspects of the universe at large, with the tremendous diffi- 
culties in the way of investigation, still present problems 
that resist solution. 

NEBULAR STARS 

Any attempt to explain the origin of the earth must be 
preceded by investigation of stellar development, and this 
in turn by inquiry into the probable formation of stars from 
nebular material. The latter is even more speculative than 
the evolution of the stars as such; and we are obliged not 
only to regard the known facts, but to consider the most 
reasonable theories that account for them, though the proofs 
yet lie on the confines of science. 

Unlike the stars that challenge the notice of the most 
casual observer, the phenomena of the nebulse are made 
known only by the combined use of the telescope, the camera 
and the spectroscope. On a clear and moonless night a good 
eye may perceive some of these objects as irregular patches 
of dimly diffused light, which reveal nothing of their true 
character. Even observation through powerful telescopes 
finds little more. Only prolonged exposure of the photo- 
graphic plate, far more delicately sensitive than vision, dis- 
closes the formation and structure of these obscure objects. 
Thus they are permanently recorded for comparison and 
analysis. Owing to their peculiar fitness for photographic 
reproduction, they permit excellent pictures to be made. 
Some of them may be found in most works on astronomy. 
Examination of the various and spectacular forms they 
reveal will engage every thoughtful mind unfamiliar with 
what may be styled the protoplasm of the cosmos. 

The spectroscope gives the explanation that the photo- 
graphs suggest. It shows these cosmic clouds to be com- 
posed, for the most part, of the familiar elements of matter 
in a highly diffused state. If they are the disintegrated 
materials of former bodies, this is precisely the character 
they would disclose, If they are the diffuse beginnings of 



28 OUR WORLD 

future stars, their number should be very great; and so it 
is. As the stars show great diversity of age and state, 
the nebulae — if such be their source — should manifest a 
similar variety of condition; and so they do. From the 
multifarious character and composition of the stars, there 
should be a like diversity of nebular types ; and such is the 
fact. These types, as might be expected from their tenuous 
nature, are not so readily classified as the stars, yet they 
fall into fairly definite order. As with the stars, the char- 
acteristics of some of the nebulae are not fully understood ; 
but enough is known to justify confidence of opinion that 
here are the beginnings of stellar evolution in all its variety, 
since they suggest the probability of automatic processes 
by which dark bodies, extinct in every function save that 
of motion through space, are transformed from inert but 
potential matter to renewed dynamic energy, thus entering 
upon a new cycle of solar and planetary existence. 

Between the youngest stars and mere nebulae is a class 
so plainly sharing the nature of both states that the phase 
of transition is unmistakable. These interesting objects are 
styled the Wolf-Rayet stars, from the French astronomers 
who first discerned their peculiarities. Were they stars in 
course of gradual dissolution, as some observers have sug- 
gested, they would probably appear very much as they do. 
They project various combinations of continuous spectra 
and bright bands, thus proving condensed cores surrounded 
by extensive atmospheres at high temperatures. However, 
the suggestion that the phenomena indicate dissolution has 
no substantial reason to support it, except the high rate of 
speed at which this class of stars travel. On the contrary, 
all the facts, direct and analogous, so far as they have 
been determined, point to the opposite conclusion, which is 
generally accepted. These stars, which are relatively few 
(about no are now known), are well within the boundaries 
of the Milky Way and the Magellanic Clouds. 

Apparently the phase of development preceding the Wolf- 
Rayet stars, in some instances, is that of the so-called plan- 



COSMIC PHASES 29 

etary nebulae. These objects show a greater resolution of 
their materials into a gaseous state, yet possessing enough 
consistency in the central mass to produce a more or less 
spheroidal shape, though differing somewhat from one an- 
other in form and general arrangement. In some of them 
the central mass is encircled by a well-defined nebulous ring 
or shell. The number of this class is about the same as 
that of the Wolf-Rayet stars ; but closely akin to them are 
several score of stellar nebulae, which doubtless belong to 
the same class, any difference in appearance being due to 
their greater distance. Most of them are scarcely distin- 
guishable as stars proper, because of their hazy appearance. 
Photographs, however, reveal their irregular dimensions, not 
widely extended, but quite compact, though entirely gaseous, 
as shown by the spectroscope. Like the Wolf-Rayet stars, 
the planetary and stellar nebulae evince an affinity for the 
Milky Way; the great majority are within it and the others 
not far removed. The reason for this — and evidently the 
fact is too general to be the result of mere chance — has 
not been divined. 

If all the Wolf-Rayet stars do not pass through the pre- 
liminary stage of planetary nebulae, the explanation is the 
probable difference in the conditions that produced them; 
but the conditions are supposed to differ in degree rather 
than in character. The cause is found in the most spec- 
tacular phenomena, except the great comets, beheld in the 
heavens — the Novae. As their name implies, they have the 
appearance of new-comers among the stars. Their bril- 
liant but brief appearance has been a source of wonder 
through many centuries, the first one recorded being in the 
Chinese Annals of 134 B. C. 

If a huge dark body, an extinct star, were to pass with 
great velocity through an expanse of dark nebulous matter 
(which is supposed to exist in many regions, such as the 
Coal Sack and great patches elsewhere in the Milky Way, 
obstructing the light of stars beyond) concentrated into par- 
ticles or small bodies, the impact of myriads of meteor- 



30 OUR WORLD 

like bolts would bombard the surface into incandescence — 
the sudden flare of brilliance that heralds the nova. If 
the obstruction were not resistant enough to disturb the 
internal structure, the light would soon fade away. If, 
however, the cataclysm were wrought by the collision or 
close approach of two great bodies, the immediate result 
would also be the flash-star; but the subsequent phases 
would differ. The violence in either case would cause such 
disruption and heat that one or both of the bodies would 
be dissipated into gas, and a field of irregular nebula would 
mark the scene of the catastrophe. Precisely this phe- 
nomenon has been repeatedly observed. 

Obviously, a great variety of results might appear, de- 
pending on the degree of energy awakened in the slumber- 
ing mass and on the precise manner in which the disturb- 
ance was produced. Such conceivably were the causes of 
the planetary and stellar nebulae, which, like the Wolf-Rayet 
stars, are moving with high velocities. The basis of this 
served facts are not only in accord with it, but no other 
theory is more substantial than sheer speculation; the ob- 
adequate explanation is at hand. As the novae have a most 
important bearing on the greatest of astronomic problems, 
and as they will presumably appear from time to time in 
the future as they have in the past, every resource of science 
will be applied to their investigation. It is well, therefore, 
to have sufficient understanding of the subject to appreciate 
the announcements of observations that will occasionally 
appear in the public press, which in these days is laudably 
eager for news from other worlds than ours. 

IRREGULAR NEBULAE 

Two other general types of nebulae require some notice — 
the irregular and the spiral. Both appear in immense num- 
bers and great variety. For some reason the spirals are not 
found in or near the Milky Way. The cause of this is yet 
unknown. They abound elsewhere in the firmament to the 
extent of hundreds of thousands. The irregular type appear 



COSMIC PHASES 31 

in photographs not unlike cloud formations, with shapes as 
variant and fantastic, and they are generally located in or 
near the Milky Way. Some ragged masses show fields of 
condensation aglow with heat that yield the bright-line 
spectra of familiar elements. Others are diffused beyond 
conception, some being estimated at one ten-millionth of the 
density of air. That such gaseous clouds can be heated in 
the absolute cold of inter-stellar space (-273 centigrade) 
is impossible. Yet they give well-defined spectra, displaying 
the lines of nebulium, an element seldom known in any 
other environment. It may be that the light is of an elec- 
trical order; certainly physics and chemistry have here an 
unsolved problem of the first degree. It is a fair specu- 
lation that when, if ever, a more intimate knowledge of 
this element is obtained, a strong light will be thrown upon 
the cause of its presence in nascent nebular conditions. 

That the nebulae have a direct relation to stellar develop- 
ment is apparent from the fact that a large proportion of 
them contain young stars, in which nebulium is replaced by 
helium and hydrogen. Strikingly enough, each of these stars 
is usually surrounded by more or less of a hiatus, showing 
that the nebular matter that was near it has been absorbed. 
The nebulae of the Pleiades is doubtless in the way of be- 
ing taken up by that system, which presumably had its origin 
in centers where condensation began. Some conception of 
the grandeur of this spectacle may be formed from the di- 
mensions of the cosmic field. The Pleiades are thought to 
be distant some two hundred light-years, and the radius of 
the system not less than three — six thousand times the 
radius of the solar system. 

The origin of the vast irregular nebulae is an absolute 
enigma. Since novae have not appeared in conjunction with 
them, there are no concrete facts upon which to base a re- 
liable theory of the cause. Yet the multitudes of them imply 
a very general cause, which seems to operate alike within 
and without the galactic regions. No other objects are 
permanent, and these may be assumed to indicate a phase 



32 OUR WORLD 

that had a beginning and must have an end, though the eons 
of years required for a change to be noted in any individual 
case renders detection hopeless, except by observing other 
similarly constituted objects in the initial process, should 
they appear. It may be that, inasmuch as the existing con- 
dition is not different from many known to be caused by 
novae, these irregulars were similarly produced, but before 
the era of our astronomy. Examples of the irregular type 
resembling ragged streamers having much greater length 
than breadth might seem to be best explained by the action 
of some prodigious force, as the passage of a huge body, 
after a collision or disrupting approach, along a regular 
course at tremendous speed carrying the wreck in a long 
wake behind. Others, while individually spread through a 
vast expanse, suggest a cause not continuing beyond the 
scene of a catastrophe. 

Without pursuing this subject further, it is evident that 
what is positively known is greatly exceeded by the un- 
known ; yet it may be expected as a reasonable probability 
that, if current hypotheses are well founded, phenomena 
will eventually be observed to justify them. 

SPIRAL NEBULA 

The origin of the spiral nebulae is not less baffling. They 
are known to exist in much greater numbers than the irregu- 
lar; so great is the proportion that it is even thought that 
many of the small but apparently irregular ones are really 
spiral, though the type cannot be discerned because of the 
distance. The mystery of the spirals is such that the theory 
is entertained by some astronomers that they actually are 
not nebulae, but remote systems of stars entirely separate 
from the universe to which the solar system belongs. Yet 
it is difficult to reconcile their appearance as revealed by 
numerous and excellent photographs with the idea of such 
stellar systems. Their arrangement and formation differ so 
much and exhibit so many characteristics of nebular matter 



COSMIC PHASES 33 

in an advanced state of condensation, that physical laws 
readily account for the phenomena. 

They invariably have a huge central mass in spheroidal 
form ; and in many this core is beautifully distinct and quite 
regular in outline. They exist in all manner of positions. 
Some present their entire circumference; some their lateral 
phases ; while others show all degrees of tilt to the line of 
sight. Some show a high degree of concentration in the 
plainly evident knots or aggregations of matter scattered 
round about. Others display only a faint texture in the out- 
lying parts, which are never homogeneous, but lie in strips 
or convolutions radiating in curved streamers from the 
center, like sparks from a pin- wheel. Some are right-handed, 
and some left, in their apparent gyrations. Few are near 
enough to yield clearly defined telescopic vision, yet all have 
continuous spectra from the knots, which demonstrates that 
if they are not composed of more or less solid bodies, their 
materials are gases in a high degree of condensation, in 
accord with the theory that they are stars in process of 
formation. 

If they constitute other universes, they are unlike ours, 
which has no central mass ; and in any event they would 
scarcely show rotation. On the other hand, if they are 
truly nebulae, their more distinguished parts might show 
such motion. Thus it was announced that measurements of 
two plates, one taken in 1896 and the other in 1916 at the 
Palkowa Observatory, of one the most notable spirals (in 
Canum Venaticorum, M. 51) show systematic movements 
in thirty-six nuclei or centers of condensation ; the knots in 
the outer spiral are receding from the central mass, while 
those in the eastern part of the inner spiral are moving 
clockwise toward the center. Similar movement has since 
been observed in other spirals. Recently the radial motion 
of the spiral nebulae has been calculated by means of spectro- 
grams. One is receding at the rate of 1,800 and the other 
1,300 kilometers per second. The former velocity is the 
greatest yet known for any celestial object. These facts 



34 OUR WORLD 

would seem to upset the theory that the spirals are not a 
part of our universe and indicate that they are clusters in 
process of evolution. If they are, as generally supposed, 
members of our own stellar system, we are still confronted 
with the mystery of their origin. If produced by the col- 
lision or near approach of great bodies or clusters, novae 
should result ; and a considerable number have recently been 
noted in the spirals, but owing to their great distance they 
are not conspicuous. Centuries of observation may be neces- 
sary before this and other problems of origin can offer a 
definite promise of solution. On the other hand, phenomena 
may appear at any time to confirm theory or give a new 
turn to investigation. 2 

USES OF ASTRONOMY 

Such are the outlines of cosmic evolution as now appre- 
hended. Hypotheses, of course, in so far as they have not 
been demonstrated, are provisional and must accommodate 
themselves to new facts as they are established, or give way 
to new theories that will; for science is dominated by the 
sole purpose of arriving at the truth. Behind the facts now 
known and the speculations that seem most in harmony with 
them, lies a maze of physics and mathematics scarcely con- 
ceivable by those who are not acquainted with the methods 
employed in astronomy to test and verify every fact how- 
ever slight and every principle however limited in its ap- 
plication. Every generalization is based on the accumulated 
data gathered by a succession of able men who have each 
bestowed a lifetime of aptitude and labor to some essential 
branch of research. Besides all this, the gradual perfection 
of the instruments and appliances which have been devised 
in aid of the study of astrophysics display an order of in- 
vention and mechanical skill unequalled in any other field. 
And these results have been made possible largely by the 
munificence of practical men who, having amassed fortunes 
in business enterprise, devoted ample funds to the equip- 
ment of astronomic study. 



COSMIC PHASES 35 

If the sublime science of the stars had no other result 
than to enlarge the boundaries of intellectual conceptions 
and to satisfy the innate desire to know how the universe is 
constituted, those objects would warrant the genius and 
labor devoted to them ; but the results are material as well. 
Astronomy is essentially physics; and every discovery in 
that basic department of knowledge sooner or later leads to 
concrete, practical results in the domain of industrial and 
commercial activity with its attendant benefits to society 
at large. 



CHAPTER II 
IN THE BEGINNING 

THE SOLAR SYSTEM 

THE retinue of the sun being the normal product of con- 
ditions that formed the system, similar systems — vary- 
ing with the masses of material and the application of the 
forces involved — must be attendant upon a multitude of suns 
scattered through the universe. But there is little hope that 
the probable fact can ever be demonstrated. If the present 
power of the telescope could be multiplied ten-thousand-fold 
it would not reveal planets by reflected light ; indeed, if any 
were brilliantly incandescent, they would be too small to be 
seen, because of their immense distance from us. The only 
recourse must therefore be to theory, justified by established 
facts and laws of matter. 

In 1894 the Lowell observatory was established at Flag- 
staff, Arizona, where the serenity of the atmosphere is pe- 
culiarly suited to the purpose. It was projected by Percival 
Lowell and directed by him until his death in 1917. He con- 
ceived the idea of devoting the work of an observatory, 
perfectly equipped, to the study of the solar system — 
"planetology," as he styled this division of research. The 
results of the enterprise have been worthy of the conception. 
Lowell is best known for his zealous advocacy of the theory 
that the planet Mars is an abode of life; but perhaps his 
most enduring merit is the great impetus he gave to popular 
interest in astronomic science. With a fertility of specula- 
tion, in some cases in advance of the more cautious and con- 
servative members of his profession, he possessed in a high 
degree the faculty of presenting abstruse phases of astro- 
physics in a clear and engaging way. He thus fulfilled most 
admirably the scientist's function of disseminating knowl- 

36 



IN THE BEGINNING 37 

edge, which stands close in importance to acquiring it; for 
its power is in the ratio in which it is spread. 3 

It had long been apparent to thoughtful minds, not so 
engrossed in a single aspect or department of science as to 
neglect the bearing of the others, that the solution of the 
ultimate problems can be reached only through correlation. 
If evolution be universal, every phase is a link in an un- 
broken chain from primal matter. This is the basis of 
Spencer's Synthetic Philosophy, and therefore the source 
of the potent influence, direct and indirect, which he has 
exerted upon modern thought. 

Lowell complained that text-books of science limped far 
behind the progress of knowledge, and even accused 
geologists of ignoring certain decisive facts that astronomy 
placed at their disposal. However this may be, it was re- 
served to Chamberlin, an American geologist, in conjunc- 
tion with Moulton, an astronomer, to replace the outworn 
Nebular Hypothesis with a theory of the origin of the 
solar system more in harmony with the facts known and 
the operation of physical laws. This is known as the 
Planetesimal Hypothesis, and is more widely entertained 
than any other at the present time by men of science best 
qualified to recognize any structural weakness in the 
reasoning. 

To understand this theory is indispensable to those who 
would know the most advanced opinion as to the origin of 
the earth and the system to which it belongs. And this 
knowledge involves much more than an important specula- 
tion: it requires some acquaintance not only with the 
physical conditions that now exist, but with the progress of 
physical science in recent years and the modifications it has 
compelled in previous theories devised in the absence of 
data and principles now accepted. The most elementary 
facts concerning the organization of the solor system are 
now very generally understood; but they may be usefully 
restated in connection with some other significant features 
not so commonly known. 



38 OUR WORLD 

To visualize the position of the earth and its relation to 
the sun a simple illustration will serve better than an array 
of imposing figures. Thus, if the earth were the size of an 
orange, and the sun and its distance were of like ratio, the 
sun would be a glowing globe some 25 feet in diameter, with 
the earth revolving around it in a nearly circular orbit about 
half a mile away. The most outstanding fact of the system 
is that all the planets revolve about the sun in the same di- 
rection and in nearly the same plane, which is called the 
plane of the ecliptic. This fact is conclusive evidence that 
the entire system was started at the same time and by the 
same impetus. 

The diameter of Mercury, the innermost plant, is a little 
less than Y% of the earth's. Its axis is nearly perpendicular 
to its orbit, which is quite eccentric, but its orbital plane is 
much more inclined to the ecliptic than that of any of the 
other seven planets. The period of its revolution is 88 days. 
Under the immediate dominion of the sun — the mean dis- 
tance being 36 million miles, a little more than y% of the 
earth's — tidal movements long ago extinct brought its ro- 
tation to the period of its orbital revolution, precisely as 
with our moon ; thus it always presents the same side to the 
sun. It has no atmosphere: the restraint of its gravitation 
was not great enough to prevent the dissipation of its gases. 

In size and probable constitution Venus is so nearly like 
the earth that it would doubtless be an abode of life at an 
early stage but for a physical infirmity from which the earth 
is exempt. The year is about seven and a half months of our 
time — 225 days. About two-thirds of our distance from the 
sun, the doubled power of its rays would yield a heated 
climate from pole to pole, the axis being nearly upright to 
the orbital plane. But, like Mercury, one side is probably 
bathed in the sun's torrid glow, and the other sheeted in 
perpetual ice. Too near the sun to withstand the tidal forces 
set up by its attraction, the initial rotation gradually merged 
in the orbital revolution. Great enough, like the earth, to 
have and to hold an ample atmosphere, the currents pro- 



IN THE BEGINNING 39 

duced by such unequal temperature would have removed 
most of the evaporated moisture from the warm to the 
frigid side, where it would be deposited as ice. Such, at all 
events, are the generally accepted conclusions of the planet- 
ologists of Flagstaff, but they depend on the time of rotation, 
which has not yet been conclusively determined, and is still 
the subject of controversy. 

That a planet, even so favorably situated as Venus, should 
not at some stage of its history be an abode of life is con- 
sistent w T ith other orders of phenomena. There can be no 
phenomena that are not produced ; hence they cannot be in- 
consistent with causes. If the origin and evolution of life 
are normal results of suitable conditions, those precise condi- 
tions must first exist. Whether or not a planet shall be 
productive of life depends not on the system to which it be- 
longs but on its individual conditions. Nature is no doubt 
as regardless, so to speak, of what proportion, if any, of the 
members of planetary systems shall beget life as of the pro- 
portion of embryos that become adult, and may be as 
prodigal of one as of the other. Yet the conditions of life 
may be far more elastic than positive knowledge has demon- 
strated. These considerations apply with peculiar force to 
Venus on one hand and to Mars on the other. 

The orbit of Mars, the outmost of the four inner planets 
of the solar system, is slightly ellipse, the mean distance 
from the sun being somewhat more than iy 2 times that of 
the earth and the axis is slightly more inclined. The Martian 
day is nearly 38 minutes longer than ours, and the year 
about 687 of our days, therefore the seasons are nearly 
twice as long as ours. The diameter is a little over Y% of 
the earth's ; the density about % i the volume about Yi ; 
and the surface a little less than %, without oceans and with- 
out mountains. The mean temperature is much lower, Mars 
receiving from the sun only % of the light and heat received 
by the earth. The atmosphere is much drier than ours. The 
water on the planet is supposed to be derived wholly or 
mainly from the seasonal melting of the polar snows, which 



40 OUR WORLD 

are plainly visible through telescopes of moderate power. 
The so-called canals, reported by Lowell with much cir- 
cumstantial detail, are also seasonal, waxing and waning 
with the polar caps. The greenish hue of the Martian sum- 
mer lends some support to the reasoning that the "canals" 
are strips of vegetation, stimulated by irrigation from the 
melting snows, through an elaborate system of artificial 
channels. Such a system would be a marvel of engineering 
skill and achievement, showing a high order of intellect. 
The supposition that such works are feasible, under the spur 
of necessity, is aided by the conditions that exist there. The 
surface gravity is only about %o of the earth's, so that the 
same exertion there as here would accomplish a proportion- 
ately greater result. The serious doubts entertained by the 
critics of Lowell's theories should eventually be determined : 
for the solution is probably within the ultimate resources of 
science. 4 

The four outer planets, owing mainly to their vastly 
greater size, are in a different condition from that of the 
inner four. All are largely gaseous. Their orbits are only 
slightly elliptical. Jupiter, the major member of the system, 
revolves at a mean distance from the sun of about 5% times 
that of the earth, in a period somewhat less than 12 years. 
The axis is but slightly inclined to the plane of the orbit. 
The rotation at the equator is about 9 hours and 50 minutes, 
while the polar zones are several minutes slower. As might 
be expected from such a plastic condition, the form of 
Jupiter is distinctly oblate. The diameter at the equator is 
over 88,000 miles. This immense volume implies some 1,400 
times that of the earth, though the actual mass is only 
314^ times greater. The mean density is only 1% times 
the density of water. This signifies that the external volume 
is composed largely of heavy vapors, probably metallic, for 
the temperature of the interior must be very high. The 
planet is doubtless in the last stages of incandescence, not 
brilliant enough to be luminous through its murky envelope 
and across the vast distance that separates us, at least ex- 



IN THE BEGINNING 41 

cept in small areas continually changing through movements 
from below. These characteristics account for the banded 
and variant appearance of its disc. Its brightness, therefore, 
is due to its size and its albedo or reflecting power, which 
is a little greater than that of fleecy clouds. In short, the 
chief interest in Jupiter is in the evidence it gives of the be- 
ginning of the obscurity to which all stellar bodies are 
eventually doomed. 

In all essential features, Saturn, the next outlying planet, 
bears a strong resemblance to Jupiter. Its mean distance 
from the sun is gy 2 times that of the earth, and its diameter 
about gy 2 times greater. The axis is inclined 2J degrees to 
the orbital plane. The period of revolution is 29 years 167 
days. The time and character of its rotation and its form are 
much the same as Jupiter's. The volume is about 750 times 
the size of the earth, though the actual mass is but 94 times 
greater, the mean density being about l /% of the earth's. 
Saturn is therefore composed of somewhat lighter materials 
than Jupiter, probably having a concentrated core and a 
relatively deeper envelope of gases and vapors; but, in the 
main, the two planets exhibit a very similar physical stage, 
which points strongly to unity of origin. 

Uranus and Neptune show a somewhat similar kinship. 
Both were unknown to the ancients. Uranus was discovered 
as a planet in 1781. It had been seen repeatedly before, but 
was mistaken for a faint star. Study of Uranus led to the 
discovery of Neptune. The normal orbit of Uranus was soon 
determined; but before 1845 observers noted an increasing 
irregularity which could only be accounted for by the pull 
of an unknown body. Mathematicians soon found the prob- 
able location of the stranger, and in 1846 the telescope 
readily found the outmost of the planets. The distance of 
Uranus from the sun is about 19 times that of the earth, and 
that of Neptune about 30 times. The period of one is 84 
years 7 days, and of the other, 164 years 284 days. As both 
planets shine only by reflected light little is known concern- 
ing them by direct observation. Both are markedly 



42 OUR WORLD 

spheroidal ; hence they are in a highly diffused state and in 
rapid rotation. The diameter of Uranus is somewhat less 
than four times the diameter of the earth ; the volume about 
65 times; and the mass about 15 times. In density it is of 
much the same order as Jupiter. "Without even an embryo 
core," says Lowell, "its substance passes from viscosity to 
cloud." There is no great difference in size or general 
character between it and Neptune. Both are aggregations 
of gases and vapors rather than solid materials, and doubt- 
less contain a much lower percentage of the heavy elements 
of the interior planets. Uranus has a greenish hue, caused 
by the absorption of other rays by some peculiarity of its 
extraordinary atmosphere. Indeed, the spectrum contains 
certain dark bands possibly produced by one or more ele- 
ments not known elsewhere. Another distinguishing fact 
which may have an important bearing upon the question as 
to the origin of Uranus and Neptune is the character of their 
rotation. Uranus is inclined about 98 degrees and Neptune 
about 145 degrees to the plane of the ecliptic. This means 
that their rotation is retrograde — from east to west, unlike 
that of all the other planets, though their orbital revolution 
is from west to east like the others. 

The satellites of the solar system are probably a miniature 
application of the physical laws that governed the forma- 
tion of the system itself. Mercury and Venus are moonless. 
Presumably they were too near the sun to hold moons in 
revolution about them. Our moon, proportionately to the 
size of the earth, is much the largest attendant upon any of 
the planets, and is actually larger than most of them. This 
anomaly has led to the opinion that originally the earth and 
the moon were one, separating while in a plastic state 
through rapidity of rotation, after the manner of binary 
stars. The diameter of the moon is a little more than J4 of 
the earth's, and its mass about % - Its orbit, like that of 
most satellites, is quite eccentric, the mean distance from the 
earth being 238,862 miles. Like Mercury and Venus, and 
like all the satellites so far as fact can be determined, the 



IN THE BEGINNING A3 

revolution and rotation of the moon are the same. Its sur- 
face is relatively much rougher than the earth's, many of its 
elevations being as high as the earth's highest and some even 
higher. It is scored and pitted by craters great and small, 
apparently the result of by-gone volcanic activity, though the 
cause is uncertain. This feature is one of the evidences that 
the moon was a part of the earth's primordial bulk, as other- 
wise it would not have had the heat to produce such con- 
vulsions. But the effects of the eruptions have remained 
unchanged. Too small to hold an atmosphere, the primeval 
roughness of the surface has not been worn and eroded by 
the action of air and water. There it wheels its silent course, 
the fragment of a world in which even the chemical forces 
of matter are wholly inert. And thus it w 7 ill continue until 
perchance some new cataclysm shall awaken its dormant 
energies and distribute its elements into other forms with 
different destiny. 

Mars has two moons more diminutive than their names 
would imply. Phobos (Panic) is probably somewhat less 
than 30 miles in diameter, revolving in 30 hours and 18 min- 
utes in an orbit nearly 4,000 miles from the planet. Deimos 
(Fear) is not more than 10 miles in diameter, revolving 7 
hours and 39 minutes at a distance of about 12,500 miles. 
Both are barely large enough for gravity to mould them 
into spheres ; and such is the perfect balance of gravitational 
forces that when Mars drew them from the welter of the 
beginning, their speed preserved their existance at the price 
of their freedom, the paramount law alike of planets and of 
moons. 

Jupiter and Saturn have each a large known retinue, and 
probably a still larger not yet known and possibly not dis- 
coverable because of their smallness and distance from us. 
These satellites are in themselves almost a demonstration of 
the catastrophic origin of the solar system. The great size of 
Jupiter and Saturn, their distance apart and from the other 
planets would necessarily endow them with the attractive 
power to draw a swarm of minor bodies, dispersed ma- 



44 OUR WORLD 

terial, either into themselves or within their orbital jurisdic- 
tion as satellites. Four of Jupiter's moons were among the 
first objects Galileo beheld with his primitive telescope. The 
ninth was found in 1914 upon a photographic plate, being 
otherwise invisible. Two of these moons are over 3,000 
miles in diameter. 

Saturn, like Jupiter, has nine known moons, one of them 
being about the size of Jupiter's largest. The rings of Saturn, 
the most spectacular feature of the planet, are merely sev- 
eral concentric bands of loose material — very small bodies 
or particles of matter — revolving at different speeds and 
held in their scattered positions by the counter attraction of 
the planet and the moons. The rings are about 172,600 
miles in diameter, more than twice that of the planet, but 
they are not over 40 miles in thickness, which is neither 
regular nor constant. Like most of the moons, the rings 
revolve in the equatorial plane. 

It is a fact not to be neglected that the two outer moons 
of Jupiter and the outermost one of Saturn are retrograde, 
revolving from east to west. From this the inference is 
drawn that the original motion of the planets was reverse, 
having been compelled by the pull of the sun to conform to 
its rotation. The inner moons have obeyed the mandate; 
but the outer ones, under less compulsion, have lagged be- 
hind as the greater inclination of their orbits indicate. And 
this inference is aided by the conduct of Uranus and Nep- 
tune. The former has four known satellites, and the latter 
one. Doubtless there are others which are invisible. The five 
revolve in the equatorial planes of the planets and are 
therefore retrograde. 

Between the orbits of Mars and Jupiter is an expanse of 
about 342 million miles long supposed to be untenanted, but 
now known to be the course over which the planetoids pur- 
sue their chase around the sun. They range in size from 
masses 500 miles in diameter to the point of disappearance. 
Their paths are generally far more eccentric than the 
planetary orbits, and some of them display an equal disre- 



IN THE BEGINNING 45 

gard of the plane of the ecliptic. Three of them intrude 
within the orbit of Mars and one, Eros, periodically comes 
nearer to the earth than any other body except the moon. 
On the other hand, four pass beyond the orbit of Jupiter. 
However, they all revolve from west to east and rotate like- 
wise. The smaller ones resemble gigantic boulders torn from 
their surroundings and are too small to be drawn into spher- 
ical form. 

It is not to be doubted that besides the few hundreds 
catalogued, there are myriads of others too small to be 
seen, like the debris of some vast catastrophe, strewn 
through the space in which they circle. Their somewhat 
erratic movements are due to their smallness and the di- 
verse attractions to which they are subject. The conditions 
resemble those which hold the components of Saturn's rings 
from combining into one or more aggregations of satellite 
size. Yet if all the planetoids known were merged into a 
single body, it would not much exceed %o of the moon's 
mass. 

Comets, having lost the terror they formerly inspired, 
have gradually assumed their true character as minor as- 
tronomic phenomena. Positive information concerning them 
is still limited ; but enough is known to afford an explanation 
of their origin, nature and conduct. Certainly the great ma- 
jority are as native to the solar system as any of its members. 
While it is possible that some of them may have been picked 
up by the system during its long passage through space, the 
evidence proves that most of them have not. Although in 
many instances they deviate from the plane of the ecliptic 
and are retrograde, they often observe the direct sense of the 
system. The latter tendency is explained by the tenuous 
composition of comets and the ease with which their motion 
may be deflected by too near approach to the great exterior 
planets. Indeed, Jupiter has caught and permanently held 
within its jurisdiction some three dozen of them; and the 
other outer planets have made similar captures. This ac- 
counts for their short periods. They round the sun, but in 



46 OUR WORLD 

each instance the outer end of the ellipse is just beyond the 
orbit of the planet that has influenced it. 

There are probably great numbers of comets ordinarily 
too small to be visible. Such have been seen during eclipses 
of the sun. Those which have not been captured by planets 
travel in enormously elongated courses, some having periods 
of several hundred years; a few may not belong to the 
system, but have been overtaken by it. Their composition 
is not uniform, yet they contain no unfamiliar elements, as 
shown by their various spectra. When remote from the 
sun their form is loosely spherical — an interior nucleus con- 
taining more or less solid or condensed material, small 
bodies or particles surrounded by a gaseous envelope. As 
they approach and pass around the sun the outer gaseous 
part, which is rarified and diffused in an extreme degree 
and may contain matter in a state of impalpable division, is 
driven away from the sun by the pressure of its potent light 
and electrical repulsion. These emanations comprise the 
tail, the form depending on the nature of the material. 
During this process the head contracts and the tail increases. 
Then the order is reversed until the objects resume their 
former condition except when disrupted by the pull of the 
sun. The last great comet appeared in September, 1882, and 
is still a vivid memory to those who witnessed it. For a time 
its head was about 150,000 miles across, and its tail more 
than 100 million miles in length. While typical of comets 
generally, it was smaller than some recorded before the 
nature of the apparitions was understood. 

The chief significance of comets lies in the fact that they 
are probably the odds and ends of the cosmic mass in 
which the solar system had its origin. In the outlying reaches 
of the system, far beyond the orbit of Neptune, there may 
yet be remnants of nebulous matter from which new comets 
are recruited ; for it is well established that great comets of 
the past have been broken up and dispersed during their suc- 
cessive journeys around the sun. It is likewise known that 
meteor streams through which the earth periodically passes 



IN THE BEGINNING 47 

are in the tracks of extinct comets, the meteors themselves, 
in all probability, being the components of the once brilliant 
visitants that appalled the credulous inhabitants of the 
earth. 5 

Presumably several millions of small meteors are caught 
and consumed in the atmosphere every day. Only the greater 
ones, which are relatively few, have survived the friction of 
their rapid passage through the air. The largest known is 
the Cape York nickel-iron meteorite brought from Green- 
land by Peary in 1895, weighing 36J4 tons, now in the 
Museum of Natural History in New York City. Specimens 
of the many varieties have been analyzed, and some thirty 
of the elements, in many combinations, have been found in 
them. The composition and structure of these fragments 
and the gases occluded in them are such that they must 
have been incorporated in a great body or bodies afterwards 
shattered by powerful forces ; otherwise the heat and pres- 
sure necessary to form the concrete masses of which they 
were a part could not have been produced. 6 

Allied with the comets and the meteors are the zodiacal 
light, the aurora and the peculiar characteristics of the day- 
light. Extending from the sun to a great distance beyond the 
earth's orbit, how much further is unknown, is a diaphanous 
mist, so to speak, produced by minute particles of matter. 
They may, for the most part, be mere atoms or molecules 
so small as to defy the microscope. The zodiacal light is a 
ghostly wedge-shaped reflection from the sun after twilight 
and likewise in the east before sunrise when the seasons and 
atmospheric conditions are favorable. Seen in the clear skies 
from the mountain-tops it stretches in a faint band around 
the ecliptic. Another similar illumination, oval in form, 
known as the gegenschein, is also sometimes observed in the 
sky on the ecliptic opposite the sun. 

This thinly diffused matter is symmetrical in its exten- 
sion, but wider along the ecliptic than deep through the 
poles. No doubt the aurora is caused by the magnetic energy 
of the sun acting upon this discrete substance. Without 



48 OUR WORLD 

it the sky would be dark at noonday, and the shadows sharp 
and deep. Aided by the molecules of the atmosphere, it 
scatters the direct rays of the sun, diffusing the glare into a 
softer and more general glow. In the upper regions of the 
air the particles are so small that they reflect only the shorter 
wave-lengths, thus illuminating the sky and tempering the 
color to blue. As the larger particles are nearer the earth 
their reflection of the longer wave-lengths of the spectrum 
yield the gorgeous tints of sunrise and sunset. Even the 
precipitation of rain, as we know it, would be impossible 
but for the agency of this impalpable dust in starting the 
condensation of the moisture in the clouds; yet the very 
minuteness of the particles soon restores them to the alti- 
tudes from which they are carried by the raindrops, through 
causes somewhat analogous to those which develop the 
comets' tails. 

The total mass of this matter is very considerable. The 
motion of Mercury at perihelion is faster than required by 
known forces. The other planets and the moon show per- 
turbations difficult to account for. This movement of Mer- 
cury was formerly ascribed to an interior planet. When it 
was determined that there is no such body, the cause of 
the anomaly was sought in the gravitational effect of the 
total mass of the cosmic dust, assuming it to be approxi- 
mately equal to that of Mercury. The true explanation is 
now asserted by the theory of Relativity. 7 However this 
may be, we may fairly infer that the diffuse material is due 
to the same cause that brought the solar system into being 
and is therefore a normal incident of planetary organization. 

THE SUN 

No feature of astronomic study has been the subject of 
such varied and profound interest as the sun. Not only the 
center of the system, the gravitational power that holds the 
planets in their courses, it is the source of every function 
that begets and supports life on the earth. Without the 
energies sustained by its light and heat, the varied conditions 



IN THE BEGINNING 49 

upon which they react, whatever may be their other poten- 
tialities, would be barren of biological results. A star among 
stars, the fellow of myriads, it measurably supplies the de- 
tails that all the perfection and refinements of astrophysical 
research cannot bring from the distant orbs. Readily amen- 
able to the resources of scientific investigation, it has richly 
rewarded the labors of science. Knowledge of its character, 
components and conditions has rapidly increased from year 
to year, until in most respects its tremendous phenomena are 
understood as intimately as any objects of laboratory study. 
For the present purpose the essential features' may be 
sketched with a brevity that gives slight token of the mani- 
fold physical researches by which the data have been de- 
veloped. 

The first fact that arrests attention is the magnitude of 
the sun as compared with the other elements of the system, 
though much smaller than many other stars of the same 
type. In constitutes 99% per cent, of the total mass. Thus 
all the planets, satellites and other matter in the system out- 
side of the sun form but %45 oi the whole. This fact is of 
prime significance in any speculation as to the origin of the 
earth. 

In volume the sun is more than a million and a quarter 
times larger than the earth ; but as its mean density is only 
1. 41 as compared with w T ater, the mass is about 333,000 
times greater than the earth. It inclines about 7 degrees to 
the plane of the ecliptic. As may be implied from its physical 
character, its form is slightly oblate. The rotation at the 
equator — 24.6 days — is more rapid than that of the parts to- 
ward the poles. The materials and condition of the interior 
are unknown except by inference, but the deductions may 
be regarded as reliable. By no possibility can any part of 
this huge body be composed of solid matter. The surface 
temperature is some 6,000 degrees centigrade. The far in- 
terior is of necessity vastly hotter. In the presence of such 
heat, enormously surpassing the highest degree that can be 
produced in an electric furnace, the materials must be in a 



50 OUR WORLD 

gaseous state — compressed, indeed, into a condition re- 
sembling liquid, but still possessing the indefinite expan- 
sibility of gases. 

Most of the chemical elements are distinctly present in 
the sun, and it is probable that all exist there, actually or po- 
tentially. The number identified has steadily increased in 
recent years, and the few remaining undiscovered may well 
exist in the interior regions where they would naturally as- 
semble because of their uniformly heavier atomic weights, 
if all are yet evolved. 

The paramount fact of present interest is the immense heat 
of the entire body, which largely accounts for the varied 
phenomena it exhibits; and this condition points to an 
origin in cosmic forces on a grand scale. 

The radiating surface, the photosphere, presents a gran- 
ulated appearance, commonly known as the "rice-grain 
structure/' these mottled granulations, however, being sev- 
eral hundred miles in diameter. Their peculiar aspect is 
probably due to their uneven heat and radiance. Dark 
patches, the "sun spots," variable in number and location, 
but never at the equator or near the poles, are usually pres- 
ent, traveling across the disc with the rotation of the sun. 
The spots are surrounded by "faculse," ragged patches more 
vividly bright than the surroundings. The prodigious vol- 
ume of diffuse gases that envelop the more concentrated 
mass is shown by the greater brilliance of the middle of the 
disc; a photographic plate well exposed at the center is 
weak at the limb or outer rim of the disc. The same cause 
produces the sharply defined limb: we look obliquely 
through a much greater depth of gases toward the rim than 
at the center. We lose the rays from yellow to violet by 
scattering and absorption. Notwithstanding this partial 
blanketing of the radiant photosphere, it has been estimated 
that each square inch of surface emits as much light as 25 
electric arcs. By experiment it has been found that the sun 
is 5,300 times brighter and 87 times hotter than the white- 
hot metal in a Bessemer converter. This intense heat and 



IN THE BEGINNING SI 

brilliance is supposed to be caused mostly by repeated radia- 
tion rather than by vertical convection currents. 

Covering the entire photosphere is a relatively thin 
stratum of gases, to which incandescent hydrogen gives a 
scarlet hue. This is seen as a ring around the limb during an 
eclipse, and is therefore termed the chromosphere. From 
its irregular outline and numerous jet-like prominences it 
is evidently at all times in a state of violent agitation. They 
usually leap to a height of 5,000 or 6,000 miles, but often 
mount to 100,000 miles and sometimes much higher, assum- 
ing many different forms, because of the nature of the 
gases composing them and the velocity with which they are 
projected from the seething mass below. This velocity is 
sometimes as high as 300 miles per second. While the dis- 
plays are not dependent upon the sun spots, they are violent 
and extensive in connection with them. Between the photo- 
sphere and the chromosphere is a very thin stratum of some- 
what less heated gases, known as the "reversing layer," ow- 
ing to the effect it has upon the spectrum. Outside of all 
this is the corona, a tenuous pearl-hued envelope, visible 
only during a total eclipse of the sun. This appears to be 
more uniform in its extension when the sun-spots are at 
their maxima ; at other times it is very irregular in its mani- 
festations. Comets pass through it without apparent ob- 
struction or commotion. Whether purely gaseous or partly 
meteoric dust, its texture must be extremely diffuse. Its 
luminescence is probably electrical, like the aurora, and re- 
flected light from the sun rather than incandescence. 

A sketch of the sun cannot well omit some detailed notice 
of the spots, which may eventually prove an important factor 
in meteorology, the science of the weather. A spot consists 
of a dark interior, the umbra, surrounded by a less dark 
fringe, the penumbra. Being less brilliant than the main sur- 
face of the photosphere, the spots appear dark by contrast. 
They are of varied extent, the larger ones often having a 
diameter of 40,000 miles or more. They may appear singly, 
but generally in groups, as one or more large spots together 



52 OUR WORLD 

with several smaller ones, all having the same character- 
istics. They are unstable in size and duration — appearing 
quite suddenly, rapidly expanding to their maxima, then 
contracting until they vanish, absorbed by the photosphere. 
Their average duration is from two to three months; but 
this is subject to many exceptions. Spots may come and go in 
the course of a day ; some have lasted a year or more. They 
may combine and divide, disappear and immediately reap- 
pear. The most fixed and definite characteristic is the regu- 
lar cycle of their smallest and greatest number. This period 
covers about 11% years though varying from 7 to 16. The 
interval from minimum to maximum is invariably less than 
the reverse. That the maxima are attended by certain ter- 
restrial phenomena is now well established. The auroral dis- 
plays are then the greatest ; changes in the earth's magnetic 
field are the most marked ; and the prevailing temperature is 
lower. It is quite significant that the extent of the polar 
caps of Mars is amenable to the same alternations of the 
sun's mean temperature. Thus the statistics of future ob- 
servation may lay the foundation for principles of meteor- 
ology of practical service in the affairs of the world. 

According to the prevailing opinion of the ablest students 
of solar phenomena, the cause and development of the spots 
are proximately due to local changes of temperature, fol- 
lowed by the normal physical and chemical action of the 
matter involved. The faculae are highly heated areas, pre- 
sumably produced by the accumulation over them of gaseous 
matter, prominences of the chromosphere or greater density 
of the corona, that somewhat impedes their radiation. The 
resultant heat causes expansion below; and the reduced 
pressure causes the formation of vortices, which probably 
take a shape and motion similar to that of water-spouts at 
sea. As the matter rises the tendency would be to impel ro- 
tation, the movement being in the form of a spiral from 
within outward. As the flux approaches the limb the tem- 
perature lowers by the expansion of the mass. The outer 
center of the vortex would tend to produce a vacuum draw- 



IN THE BEGINNING S3 

ing in the high-level hydrogen of the chromosphere and its 
prominences. As the equilibrium is restored the spots con- 
tract and disappear. They are invariably the centers of 
powerful magnetic fields. The vortices apparently operate 
as huge dynamos. In rapid rotation the friction of dis- 
similar materials and other physical causes are supposed to 
give rise to great charges of electricity. On reaching the sur- 
face these currents manifest themselves in the magnetic 
effects conspicuously incident to the maxima of sun-spot 
activity.® 

These conclusions are the gradual results of long and pro- 
found investigation ; and for the most part they are logical 
deductions from a multitude of separate facts revealed by 
the spectroscope. Much, of course, remains to be learned, 
particularly the cause of the periodical changes, the nature 
of the corona and the areas of the faculse. But that all will 
ultimately yield their secrets may be reasonably expected. 
They are unquestionably the normal phases of stellar his- 
tory. The fact is highly significant that the spectra of the 
sun-spots are almost identical with those of the old red stars. 

Such are the external aspects of this great body. The 
difficult problem of the duration and stability of its existing 
energies will be most profitably considered in their relation 
to life, past and present, after some review of the consti- 
tution and conduct of matter. With this survey of the prin- 
cipal facts concerning the solar system, it now remains to 
present the explanation of its origin according to the 
Planetesimal Hypothesis. 

THE FAILURE OF THE NEBULAR HYPOTHESIS 

The definite conception that the solar system is the prod- 
uct of evolution apparently originated with Kant, the phil- 
osopher, when he was a young man. So early as 1755, when 
the idea of evolution in any phase of nature was revolution- 
ary and abhorrent, he sought the origin of the sun and its 
system in the condensation of elemental matter in a cold and 
diffused condition, the sun around a central nucleus and the 



54 OUR WORLD 

planets and moons around outlying and smaller centers. His 
ideas, however, were valid only as a loose generalization. 
Yet it was half a century before Herschel's remarkable 
studies of the nebulae and long before some of the most im- 
portant dynamical laws were discovered, even before the 
atomic theory of chemistry was conceived. He assumed that 
an initial mass of gaseous matter at rest would of itself, 
without external force, develop rotation ; this is now known 
to be impossible. Some years later, after the announce- 
ment of the principle that heat is produced by the compres- 
sion of gases, he attributed the heat of the sun to its gradual 
condensation, a process that must eventually come to an 
end, as already demonstrated by the planets. About a cen- 
tury afterward, the theory was established by Helmholtz 
and is now accepted as a fundamental truth, with the addi- 
tion in recent years that the process is extended by the dis- 
solution of radioactive substances. Kant also maintained 
that tidal effects would retard rotation and finally bring the 
planets to the status of the moon, continually presenting the 
same face to the center of the gravitational force. "I seek," 
said he, "to evolve the present state of the universe from 
the simplest conditions of nature by means of mechanical 
laws alone. ,, His conceptions were magnificent and far in 
advance of his time. It has been the function of science in 
this as in other cases of brilliant generalization, which have 
usually been little more than shrewd guesses, to find the 
flaws and discover the true mechanism by which the ulti- 
mate results were accomplished. 

In 1796, Laplace published a popular work on astronomy, 
which had a long vogue, due to his eminence in that branch 
of science. In the last of a series of notes at the end of the 
volume he proposed the explanation ever since known as 
the Nebular Hypothesis to account for the origin of the 
solar system. He was unaware of Kant's writings on the 
subject, and was doubtless prompted by Herschel's discov- 
eries in relation to the nebulae. There is no reason to sup- 
pose that he considered his idea as very important ; indeed, 



IN THE BEGINNING 55 

he remarked that it should be received "with the distrust 
with which everything should be regarded that is not the 
result of observation and calculation. " 

The hypothesis was that the solar system had evolved 
from a nebula of heated gases extending beyond the pres- 
ent orbit of the outmost planet, the whole mass being in 
slow rotation at an angular rate, like a revolving solid. The 
mass was in equilibrium through the expanding forces of 
heat and rotation and the contracting force of gravitation. 
As the heat was reduced by radiation the size diminished 
and the speed increased. The speed at length became so 
great as to disengage an outer ring, which retained its 
equilibrium, continuing to rotate as a solid, while the main 
mass contracted. By the repetition of this process ring after 
ring was thrown off until only a central body was left. The 
nebulosity of the rings not being uniformly distributed, 
broke into fragments, all the parts of each ring eventually 
coming together as one mass. These several masses, except 
those forming Venus and Mercury, in turn repeated the 
process, thus developing the satellites, save only in the case 
of Saturn, whose rings for some reason did not coalesce, 
but arranged themselves as solid matter instead of a moon 
or moons. 

Such was the extraordinary hypothesis that for a century 
commanded unquestioned acceptance. Laplace, like Kant, 
was impressed by the assumption that all the satellites re- 
volve around the planets from west to east nearly in the 
common plane of the solar system. He was apparently un- 
aware that Herschel had announced that the two recently 
discovered moons of Uranus were exceptions to the rule. 
This was the first shock to the Nebular Hypothesis, which 
became a fatality by the irreconcilable fact that not only 
eight moons, but two of the planets themselves, are prac- 
tically retrograde. 

Other elements of the problem proved as refractory. If 
the materials of the system originally existed as gases dis- 
tributed uniformly they would have been several hundred 



56 OUR WORLD 

million times more rarified than the air we breathe. With 
such a condition the abandonment of successive rings to 
form the planets and the planetoids would have been impos- 
sible. But if such rings could have been formed the inner 
parts would have moved faster than the outer ones ; thus the 
rotation of the planets when finally formed would of neces- 
sity be retrograde. Such a ring could not rotate as a solid ; 
physical laws require that each constituent of such a gaseous 
ring move independently of other particles. If the inner 
ring of Saturn were produced according to the Nebular 
Hypothesis, the period of its revolution would be greater 
than that of the planet : it is only about one-half. The same 
principle would apply to the inner moon of Mars : its period 
is only about one-third of the planet's rotation. The theory 
would also require that the planetary orbits be nearly 
circular: they are all eccentric, particularly that of Mercury 
which should be nearest to a perfect circle. Not less incon- 
sistent is the inclination of the sun to the plane of the sys- 
tem: if the theory were valid, the axis should be perpen- 
dicular to the plane. 

Of all the objections to the Hypothesis, perhaps the most 
conspicuous is its flagrant violations of one of the imperious 
laws of celestial mechanics, the conservation of the moment 
of momentum, as it is technically and imposingly styled. 
"Momentum," says Lowell, "is the quantity of motion in a 
body. It is the speed into the number of particles or the 
mass. Moment of momentum denotes the rotary power of 
it around an axis. It can neither be diminished nor in- 
creased. It is the one unalterable thing in a universe of 
change. What it was in the beginning of a system, that it 
forever remains. By mutual action of the particles on one 
another, by contraction, by tidal pulls, and so on, some 
energy of motion is constantly being changed into heat and 
then dissipated away. Energy of motion, therefore, is slowly 
being lost to the system, and the only stable state for the 
bodies composing it is when the energy of motion has de- 
creased to the minimum consistent with the moment of 



IN THE BEGINNING 57 

momentum. Our whole system is evolving in such a way as 
to lessen its energy of motion while keeping its quantity of 
motion unchanged." 

Considering the relative mass of the sun as compared with 
the remaining matter in the system — over 99 per cent. — fully 
96 per cent, must have been condensed in the nucleus at 
the outset. The orbital velocity of Mercury is about 45 
kilometers per second, hence the sun's equatorial velocity 
should now be at least 400 kilometers per second, in order 
to satisfy the constancy of the moment of momentum : it is 
only 2. Other discrepancies might be stated ; but these suf- 
fice. The data of the solar system and the infirmities of the 
Nebular Hypothesis thus afford very tangible indications of 
the character of the forces requisite to produce the system 
as it is. 

THE PLANETESIMAL HYPOTHESIS 

Late in the eighteenth century, Buffon, the versatile 
French naturalist, suggested that the solar system was the 
result of a huge comet colliding with the sun. Like most 
of his theories, this comes well within Spencer's observa- 
tion that error is generally the "adumbration of a truth." 
Its chief merit was that it was too heretical for consideration 
at that period. Later on it was discarded into the limbo 
of physical impossibilities. The germ of the idea long after- 
ward took the form of stellar collision. This conception 
proved more fertile. At first the results were little more 
than bizarre guesses ; but when at length the perfection of 
the photographic dry-plate, in 1886, began to reveal the 
features of the spiral nebulas, the idea gradually acquired 
a more strictly scientific basis. 

Astronomers have ever been conservative. The essential 
nicety of their calculations and the necessity for the utmost 
precision in all their work naturally beget a cautious and 
deliberate temper of mind that views most theories with 
rather obstinate suspicion, demanding very cogent demon- 
stration. It is easier to jump to the conclusion that the 



58 OUR WORLD 

spirals are produced by the impact or pull of stellar masses 
than it is to account for the collisions and the magnitude 
of the phenomena. It is obvious that the great variety of 
nebular forms, if caused in some such manner, might be 
due to the many angles of approach by the colliding bodies 
and the degree of the impact; or, if not actual collisions, 
to the infinite degrees of possible proximity to one another. 
The subject is again referred to because of its immediate 
bearing on the hypothesis. Chamberlin first proposed in 
1901, and later, with the aid of Moulton, brought to its 
present form. However, the hypothesis is necessarily a 
special one to fit the organization of the solar system, which 
is a small affair as compared with thousands of the spiral 
nebulae. 

The earlier theories started with the convenient exist- 
ence of a medium without effort to explain how it might 
have been brought to a condition suitable for evolution. 
The Planetesimal Hypothesis, on the other hand, accounts 
for the medium as well as the evolution, as successive stages 
through the operation of normal physical laws and in a 
manner largely acceptable to astronomic science. It as- 
sumes the sun to have been a body somewhat greater than 
at present and in a more diffuse state — a much younger 
star. At the critical juncture another body approached it 
in a path lying at the same angle as the plane of the eclip- 
tic, which was thus established. When the approach was 
near enough a disruptive pull began. The effect of such 
a sudden and powerful disturbance is supposed to have 
been similar to the internal expulsions now witnessed at the 
sun's limb, but on a vastly greater scale owing to the ex- 
ternal attraction. When the first great bolt shot outward, 
the immense tide it occasioned resulted in a similar ejection 
from the opposite side. This rapid alternation of projec- 
tiles continued during the short time the two bodies were 
within effective distance of one another. The matter thus 
drawn from the sun was given sufficient momentum to 
hold it from falling back upon the sun and thus arranged 



IN THE BEGINNING 59 

itself into a variable form similar to that of a typical spiral 
nebula. 

As to the character of the intruder even conjecture is 
silent. It might have been larger or smaller than the sun, 
and its rate of speed faster or slower. Certainly the result 
of the encounter might have been worse. As it was, the 
other body apparently made precisely the right approach 
in proportion to its mass to enable the sun to yield up 
enough of its surplus to furnish forth its retinue. With 
a very slight difference in the circumstances the subject 
would not now be under discussion. 

The sequel is full of intricate detail, elaborated with 
painstaking attention to the principles of physics and calcu- 
lations of mathematics. The salient aspects will answer 
here. The greater part of the resulting nebula was at first 
contained in knots or nuclei, which continued gaseous, but 
from their ampler mass were better able to retain their 
original heat. Of these the larger became nascent planets, 
and the smaller their satellites. Distributed throughout 
the entire system was the remaining matter in a more or 
less dispersed and finely divided state. All revolved about 
the sun in markedly eccentric orbits. The larger masses 
gradually gathered into themselves the adjacent matter ex- 
isting in bodies too small and therefore without the mo- 
mentum to resist gravitation. The combined effect of this 
would have been to average their orbits. This caused the 
paths of the planets gradually to assume their more circular 
form. The principle is well illustrated by the variety of 
eccentricity displayed by the orbits of planetoids. 

The chief credentials of the hypothesis are its satisfac- 
tory explanation of the general sense of the system, the 
formation and motion of the satellites, and the unfailing 
deference to the constancy of the moment of momentum. 
There are, indeed, some irregularities and apparent anoma- 
lies not yet explained, but the hypothesis is so flexible 
that additions or modifications through new discoveries and 
deductions do not seem likely to impair its general validity. 



60 OUR WORLD 

One difficulty is the peculiar distribution of the masses 
of the planets. Lowell pointed out the suggestive fact that 
the arrangement of the moons of Jupiter and Saturn is 
analogous. This tends to show an underlying cause that 
applies to all such cases. The four outer planets contain 
225 times as much matter as the four interior ones and 
the planetoids combined. But they are composed of much 
lighter materials than the inner ones; hence the inference 
that they were derived from the exterior and lighter parts 
of the sun's mass, the smaller and denser planets being 
drawn from the heavier materials within. 

Another difficulty that awaits solution is the diverse 
inclinations of the axes of the planets to the plane of the 
system. It is remarkable, though entirely possible, that the 
disturbing body should have approached the sun at so small 
an angle to its equatorial plane, as indicated by the sun's 
inclination of only 7 degrees; for it is not probable that 
a force only strong enough to dislodge less than one per 
cent, of the sun's mass could have seriously affected its 
axial position. The variety of the planetary tilts increase 
the perplexity, but without placing the hypothesis in jeop- 
ardy. The differences in orbital eccentricity may be fairly 
attributed to the varied distribution of the materials that 
entered into the formation of the planets and the circum- 
stances that governed the final result. 

The fact that the equatorial region of the sun rotates 
faster than the other latitudes is ascribed to the falling 
back of material lifted out for a short distance, thus caus- 
ing a forward tide that gave a powerful impetus to the 
contiguous belt. While this is regarded as possible, pre- 
cisely the same conditions are observed in Jupiter and 
Saturn, and are therefore supposed to be due to a common 
cause. "The most plausible explanation of this curious phe- 
nomenon," says Campbell, "is that great quantities of mate- 
rials originally revolving around the sun and each of the 
planets have gradually been drawn into these bodies, by 
preference into their equatorial areas, such masses of mat- 



IN THE BEGINNING 61 

ter moving in orbits very close to those bodies must have 
traveled with speeds vastly higher than the surface speeds 
of the bodies." This suggestion, if valid, would seem to 
militate strongly in favor of the Planetesimal Hypothesis. 
Recently the theory has been proposed that the phenomenon 
is due to convection currents. This explanation applies to 
all bodies in which such currents are possible; and it also 
accounts for the belts around Jupiter and the confinement 
of the sun-spots to the equatorial region. 

The origin of the comets is left a baffling enigma, though 
the attempt is made to explain it on the theory that splashes 
of the original matter were driven away at diverse angles 
to the plane of the primordial nebula, 

THE JUVENILE EARTH 

The astronomic phases of the hypothesis, while funda- 
mental, are but preliminary to its practical bearing on geo- 
logic history before the Archeozoic Era. It is estimated that 
the amount of nebulous matter originally in the nuclei was 
from one-third to one-fourth of the whole. Thus the earth 
at the outset was some 30 or 40 per cent, of its present size. 
It would not have been possible for so small a body to 
retain heat enough to keep it in a molten condition for a 
very long period. That it is not so now, despite the high 
degree of heat produced by pressure, is generally accepted 
for several reasons deemed conclusive. With this beginning, 
the planet began to grow by attracting to itself the planetesi- 
mals — small bodies or particles, into which the primal matter 
was resolved. At this stage, while such matter was abun- 
dant, the growth proceeded relatively fast and continued 
until the infall largely depleted the resources, though a 
negligible residue is yet seen in the meteors on every clear 
night. The other planets, of course, were enlarged in the 
same way, and the entire system steadily approached a 
stable organization. 

Such was the foundation of the lithosphere. Concur- 
rently with it, the hydrosphere and the atmosphere were 



62 OUR WORLD 

built up in the same way. The gases composing them 
were distributed through the constituent matter and were 
collected along with the other elements and combinations 
entering into the accretion until likewise the supply was 
exhausted. Thus the seas were a gradual accumulation, 
first pouring into the oceanic basins and gradually rising 
until they nearly enveloped the globe. Ere long external 
disturbance through internal shrinkage and readjustment set 
in ; volcanic action began its transformations ; and the great 
triumvirate of natural processes in ceaseless interaction 
were at work in preparing the tenantless earth as an abode 
of life. 

This is quite unlike the picture usually sketched under 
the influence of those conceptions of the beginning which 
had hitherto prevailed and are still general : a globe once 
molten, but cooled enough to allow the steaming oceans to 
form, dimming the sun with their dense vapors, bringing 
forth its sightless creatures and leafless vegetation during 
an eon of twilight, without change of seasons or variety 
of scene — a world of misty gloom and cheerless monotony. 

The existing physical condition of the earth must neces- 
sarily guide any speculation as to the manner of its forma- 
tion. The normal density of iron is 7.8, on the scale of 
water. The average density of rock formation is about 2.8. 
If these were combined half and half the result would be 
5.3. The mean density of the earth being 5.5, it is a fair 
inference that the chief ingredient of the interior structure 
is iron, which is known to exist in abundance very generally 
in stellar bodies, throughout the universe. If the exterior 
of the earth were a shell enclosing a molten core, the tidal 
effects would be prodigious in the shell itself. On the other 
hand, if the entire earth were absolutely rigid, the tides 
of the ocean would be much greater than they are. The 
fact is that the globe is elastic without distortion ; it yields, 
but at once regains its normal form. It responds precisely 
as though its rigidity were somewhat greater than that of 
solid steel. Again : there is an oscillation of latitude of 



IN THE BEGINNING 63 

points on the earth's surface. These variations pass through 
their principal cycle in a period of 427 days, the entire earth 
oscillating slightly during this time. If the earth were ab- 
solutely rigid, the period would be 305 days ; if exactly as 
rigid as steel, 441 days. Thus the results are in practical 
accord. 

The distribution of the more external materials of the 
globe is far from uniform in density. This is shown in 
several ways. The magnetic poles are quite distant from 
the poles of rotation, and they are not directly opposite to 
one another. Likewise the lines of equal magnetic in- 
tensity are very irregular over the earth's surface. Deflec- 
tion in the direction of the plumb-line and changes in the 
force of gravity also indicate that the outer strata are of 
unequal density down to a depth of 122 kilometers. Below 
that level the density of concentric regions appears to be 
quite uniform. The first waves from a distant earthquake 
come directly through the earth, and the speed is greater 
directly through the center. The change of speed is gradual 
from the center outward, showing that the density is greatest 
at the core. 

All the evidence shows that, while the earth is now en- 
tirely solid or acts as such, it was not always so. When 
the nucleus was in more or less molten state the denser 
materials gravitated toward the center and therefore devel- 
oped a more homogeneous character. The internal heat, 
now due wholly to pressure, increases at the rate of i° 
centigrade for every 30 meters. If this rate is maintained, 
the heat at a depth of sixty kilometers would be sufficient 
to melt platinum, the most refractory of known metals ; 
but fusibility decreases with pressure. Thus at a great 
depth the materials could not melt, though they would in- 
stantly liquify if the pressure were removed. 

Such data tend strongly to confirm the Planetesimal Hy- 
pothesis. The outer regions of the globe during geologic 
time were never in a molten condition, except where they 
have been affected by volcanic action. The accretions were 



64 OUR WORLD 

not of that character, nor were they of uniform composi- 
tion. This accounts in part for their varied density and 
the diversity of the materials. The same general cause is 
held to explain the characteristic difference between the 
northern and southern hemispheres. Much the greater part 
of the continental areas lie to the north and are therefore 
supposed to consist of somewhat lighter materials. The 
existing land of the Antarctic is of a later geological devel- 
opment, and doubtless exerts a decisive influence upon 
present climatic conditions by obstructing or diverting the 
main oceanic currents. 

An important feature of the hypothesis is its explanation 
of the continental formations. The exposition of the process 
is one of the most admirable stages of the entire argument 
and has met with very general acceptance by geologists. It 
is essentially one of dynamics. Only a few of the leading 
considerations may be referred to here. The original rate 
of the earth's rotation was probably much higher than 
during purely geologic time, oscillating until the growth of 
the planet was substantially complete and equilibrium was 
obtained. This would have caused stress and strain. When 
the rotation slackened, the equatorial tract would tend to 
sink and be compressed, while the polar parts would rise 
and suffer tension. Between the rising and falling tracts 
lay fulcrum zones, not far from 30 degrees North and South 
Latitude, which would neither rise nor fall. It is assumed 
that a sort of segmentation would follow along the most 
natural lines. This would roughly divide the circumpolar 
areas into three great centers of triangular form starting 
from the poles and resting on the fulcrum zones. The weak 
and strong segments would assume antipodal positions. The 
heavy and rigid sub-oceanic cones would stand opposite the 
lighter and yielding continents with an area of about two 
to one. And this is precisely what happened. The emboss- 
ment of North America is opposite the basin of the Indian 
Ocean ; of Australia, opposite the basin of the North Atlan- 
tic; of Africa, opposite the Central Pacific; of South Amer- 



IN THE BEGINNING 65 

ica, opposite the western extension of the North Pacific; 
and so on. Thus the three great oceanic abysses appear 
not only to have crowded aside the continental masses, but 
to have joined in thrusting toward the earth's center. 

It should be remarked that this work was accomplished 
during the juvenile history of the globe. If the rotation 
had slackened during geologic time the equatorial region 
would have crumpled and the polar areas stretched. This 
would have raised mountains in the torrid zone and leveled 
the higher latitudes. Such differential effects do not exist ; 
hence it is to be inferred that sensible changes of that nature 
have not occurred during the entire stage of normal geologic 
transformations. 

Long before the general alignment of the continental 
platforms was determined and during the later phase of 
planetesimal accretion volcanic agencies began their work, 
the radio-active elements probably being a leading factor. 
The readjustment of the mixed materials of the mass tended 
to press outward the lighter ingredients in much greater 
proportions than the metals and metallic alloys. In this 
manner the heavier matter would gravitate toward the in- 
terior, which became more and more rigid while the crust 
became more amenable to movement and transformation. 
"The inner reorganization of the juvenile earth," says Cham- 
berlin, "is therefore pictured as a process that affected per- 
vasively the whole interior of the earth, preserving effect- 
ively the solid state of the main mass and progressively 
increasing its average rigidity, while at the same time it set 
free and forced toward the surface, stage by stage, the 
lighter and more mobile material. The mixed states of 
the meteorites, our best guide in the matter, do not encourage 
the notion of complete segregation." 9 

Such are the outlines of the Planetesimal Hypothesis. 
Geology had reached the uttermost limit of its researches 
and had scarcely arrived at the horizon of primordial life. 
The Nebular Hypothesis had collapsed, and the vast chasm 
between the earth's origin and the condition to beget life 



66 OUR WORLD 

remain unbridged. The need for explanation was urgent, 
and the progress of physical science had supplied the means. 
The result was worthy of the diversified knowledge and 
profound deductions that achieved it. That the structure 
is finished and invulnerable is far from certain. It is not 
unlikely that the theory will undergo modification and 
amendment of detail, especially as to the inception of the 
system, through the long process of searching analysis to 
which it will be subjected in the light of advancing knowl- 
edge; but, if fundamentally sound, as it now appears to 
be, its essential flexibility would bear any strain that may 
be placed upon it. In any event, acquaintance with the 
process of evolution, it portrays, is indispensable to every 
mind that would grasp the foremost thought of the age. 



CHAPTER III 

THE GEOLOGIC RECORD 

PROCESSES 

THE diameter of the earth at the equator is 7,926.57 
miles, nearly 27 miles greater than the diameter 
through the poles, the difference being caused by the cen- 
trifugal force of the daily spin. One-half of the total vol- 
ume of the atmosphere lies within an altitude of ^A miles. 
In an increasingly rarified state it may reach to several 
hundred miles, as may be seen by the combustion of mete- 
ors, which travel at such high speed as to cause tremendous 
friction with the air. Displays of the Aurora, which de- 
pend in some degree upon the atmosphere, have been esti- 
mated to extend some 500 miles upward. The height of 
the loftiest mountains and the greatest depth of the oceans, 
at a few points, are each somewhat more than 5 miles, meas- 
ured from the sea-level. Relatively to the size of the earth, 
therefore, the surface is quite smooth and the oceans but 
a film. The changes wrought in the original crust by the 
action of natural forces have been but minor products of 
greater changes within; yet these details form the graphic 
record of the vicissitudes through which the globe has passed 
during many millions of years. 

The age of the earth from the genesis of the solar sys- 
tem to the appearance of life cannot be estimated with any 
degree of confidence ; but from other phenomena and the 
enormous stretch of time necessary to produce transforma- 
tions on a great scale, it may be implied that the time re- 
quired to bring the earth from an incandescent stage to 
one fit for the existence of life was greater than that cov- 
ered by its subsequent history and may have been many 
times greater. 

67 



68 OUR WORLD 

Long before the period of historical geology opened the 
agents of crustal transformation had began their work. 
Great areas of level surface alternating with rocky heights 
and lesser irregularities were subjected to the weathering 
effects of the elements in the same manner as such features 
are affected now, but with greater intensity. The exposed 
rocks and mineral formations were eroded by air and water, 
and the disintegrated particles were blown by the winds and 
swept by the rains into the valleys and depressions below. 
Rivers, then as now, emptied their turbid torrents into the 
oceans, seas and lakes, depositing the sediment in the peace- 
ful depths. These deposits vary in thickness from a few 
feet to many thousands, and in extent from small to vast, 
according to their origin and the stability and nature of the 
bottoms on which they rested. As the materials were drawn 
from various sources and composed of many different ele- 
ments in many different combinations, the deposits are 
highly diversified. After such strata were laid and covered 
by others similarly produced, the enormous weight of the 
mass above expelled the water and compressed them into 
stone. The earliest ones lying at great depths below these 
accumulations were generally changed in texture by heat. 
At later periods, when marine life and decaying vegetation 
exerted their chemical reactions, other types of rock were 
produced. These comprise a substantial part of the geo- 
logical formations most serviceable to man. 

The great changes which have taken place in the crust 
of the ageing earth since transforming forces began to 
operate may be seen from the fact that at least five-sixths 
of the area now exposed contain stratified rocks of marine 
origin and probably from much of the remainder similar 
layers have been eroded. Yet it 4 is quite certain that some 
portions of the existing continents have never been sub- 
merged. While the exposed areas have changed from time 
to time, the continents have gradually assumed their present 
form and during later geological ages have apparently be- 
come stable. In other words, the so-called continental plat- 



THE GEOLOGIC RECORD 69 

forms have existed from the beginning and after repeated 
subsidence and elevation at length attained a fixed position 
and support sufficient to sustain the overlying continents 
permanently above the sea-level, especially as the continents 
are composed of materials correspondingly less dense than 
those which form the ocean bottoms — the condition of 
isostasy, as it is termed. This stable condition is the result of 
a gradual lessening of the outward flux by the thickening of 
the crust and the final adjustment of the materials within. 
This in turn is due to the gradual loss of internal heat. 
Through unknown eons the globe has been slowly cooling 
and must at last become a cosmic cinder. Fortunately for 
the existence of life, it does not depend upon warmth from 
within the earth, but from the sun, though that body, unless 
it encounters some other mass, must also in the incalculably 
distant future lose its glow and become the frigid center 
of a system whence life has long departed. 

As shown by the recurrent rise and submergence of vast 
areas, the long process of erosion and the shift and recon- 
struction of the products as sedimentary rocks were accom- 
panied by other forces and changes not less momentous. 
Perhaps the most significant fact in the whole range of 
science is that matter, whatever the kind and whether 
immense or minute in volume, acts in the same way under 
like conditions. Thus every atom in the complex of things 
has always obeyed with absolute precision the laws of its 
being. Actuated by immense pressure and intense heat, the 
various elements commingled in the earth's interior have 
been in a perpetual struggle to readjust themselves accord- 
ing to their different properties. At many stages of geologic 
history, movements so caused, together with volcanic action, 
have affected the lithosphere. Stupendous quantities of 
molten matter were ejected from below. The crust was 
rumpled, folded, cracked and dislocated. In some places 
the more ancient rocks were thrust to the surface or to 
the height of mountain ranges. Islands were thrust upward 
from the bottom of the oceans and in some cases capped 



70 OUR WORLD 

by lofty peaks. Later formations were fractured and con- 
torted and came to rest in every conceivable position. All 
this was accompanied by corresponding subsidences. In 
this manner new material was supplied for old processes, 
which continued unabated, and new depressions were cre- 
ated in which to collect the eroded sediments. In some in- 
stances the accumulated strata thus produced are miles in 
thickness. Mingled with these formations in various ways 
are the products of volcanic action. In some regions pro- 
digious quantities of molten matter were ejected and before 
cooling flowed in a more or less liquid condition over the 
surrounding surface. These areas, of course, vary in dimen- 
sions and character depending on the volume thrown out, 
the nature of the materials composing the outflow and the 
irregularities of the surface that received them. In many 
places the molten matter did not overflow the surface, but 
filled the fissures in the fractured crust, or, by lifting the 
upper strata, was forced into the intervening spaces. 

Such are the outlines of the structural processes. The 
sequence of the phenomena forms the more difficult and 
important phase of geologic science. 10 

THE SEQUENCE 

Every branch of science necessarily develops a termi- 
nology of its own. Not seldom the names of phenomena 
and things are uncouth compounds of Greek or Latin terms 
difficult to understand even by one who is acquainted with 
those languages. Once adopted they enter into the vocabu- 
lary of the science in which they are applied wherever it is 
pursued. This has the untoward result of rendering the 
language of scientists alien to the general reader. It has 
come to such a pass that experts in one branch are scarcely 
intelligible to those in another. Moreover, geology being an 
old science, shows in its terminology the marks of the stages 
through which its development has passed as plainly as the 
strata with which it deals. Geographical names, ancient 
and modern and of various origin, have come and are still 



THE GEOLOGIC RECORD 71 

coming into use as arbitrary labels that have no more in- 
trinsic meaning to the novice than the names borne by 
ocean steamers or railway coaches. To one who is not 
adept in geologic science the names alone of its many periods 
require an effort of memory discouraging to study at the 
outset. It may be that this method is unavoidable, but it 
is most unfortunate that a subject so profound in its essen- 
tials, so full of interest in its stupendous climaxes, and so 
vital to a clear understanding of the history of the human 
race should not fascinate every thoughtful mind and be 
an indispensable feature in the education of youth. 

For many years historical geology, like Christian chro- 
nology, has dated from an intermediate point. Thus it is 
divided into the pre-Cambrian and the post-Cambrian. Cam- 
bria was the Roman name for a portion of Wales, and the 
impressive word was adopted by the British geologists, who 
were then leaders in the science, as descriptive of the rocks, 
variously composed, containing an abundance of fossils of 
the earliest types then known. Although these rocks were 
discovered in Wales, they of course are found in many 
parts of the world and always exhibit the same general 
characteristics. Everything below the Cambrian was styled 
the Archean. 

The Darwinian Theory, which had received powerful but 
fragmentary support in the geologic record as then disclosed, 
gave a great impetus to further researches in that field. 
It was evident that, if the theory of evolution were well- 
founded, there must have been a long succession of living 
forms graduating downward from the highly organized 
forms that appeared abruptly in the Cambrian. This would 
imply a corresponding lapse of time and an environment 
that permitted the existence of life. The facts demonstrated 
since are in perfect accord with theory. To this result 
American geologists have in a large measure contributed. 
The means exist here in an eminent degree. Notable among 
several regions on the North American continent containing 
the oldest exposed formations is that extending north of 



72 OUR WORLD 

the Great Lakes. They have revealed evidences of such 
variety and magnitude that the Archean has been divided 
into two great eras, the Archeozoic (primitive life) and 
the Proterozoic (less primitive life), both of which have 
been subdivided into a number of lesser periods, usually 
named, according to the prevailing system, from their geo- 
graphical location and the sonority of the terms. 

THE PRE-CAMBRIAN 

The Archeozoic era is one of the present frontiers of 
positive knowledge. It is the foundation of all known geo- 
logic formations. Its depth is yet unknown, but wherever 
found it shows the same chaotic mixture of materials obvi- 
ously thrown out by prodigous convulsions, which probably 
affected more or less every part of the globe. Inasmuch 
as an enormous period must have elapsed before this era 
merged into the next, some of its multitudinous products 
had time to become weathered, eroded, removed and trans- 
formed into sedimentary rocks made crystalline by heat 
and pressure. The eruptive conditions were not constant, 
but recurred after long periods of quiescence. Thus a long 
time — many thousands of years — intervened between the 
last great convulsions of the Archeozoic and the early Pro- 
terozoic. This is shown by the unconformity (as geologists 
term it) of the line of contact between the rocks of the two 
eras. The old was worn away, and the exposed strata 
were rumpled by upheaval and subsidence, leaving a clearly 
marked and extremely irregular floor for later accretions. 

The Archeozoic has thus far revealed no fossils. Even 
if there were forms of life capable of becoming fossilized, 
the altered character of the rocks would probably have de- 
stroyed the evidence, except in a few favorable locations. 
It is beyond doubt, however, that life did exist during a 
great part of this era. Immense beds of graphite found 
there furnish ample proof. Graphite could only have been 
formed by the aid of organisms that separated the carbon 
from the carbon dioxide of the atmosphere and the waters. 



THE GEOLOGIC RECORD 73 

It is possible also that other formations, such as marble 
and certain iron ores, which are found in great quantities 
in the Archeozoic, likewise originated in the reactions of 
life. 

The Proterozoic was an era of change. Less volcanic 
than its predecessor, it was more so than succeeding eras; 
yet it exhibits all the normal characteristics of later time. 
All the evidence points to general conditions similar to 
those which have since prevailed. The materials erupted 
from below were practically the same. The atmosphere 
was essentially the same, and the waters produced the same 
effects. The extremes of heat and cold were not materially 
different, showing that the sun was not obscured by vapor 
and that its radiation was not greatly different from the 
present degree ; nor was the temperature affected by internal 
heat. Plant and marine animal life flourished, though there 
were few varieties and in the simplest forms. These facts 
appear as clearly in the geologic record as the statement of 
them appears on the printed page. 

The duration of the Proterozoic, as now defined, was so 
enormous that it probably covers two distinct eras. It is 
best known in Canada, where its great extent and economic 
importance have promoted scientific investigation. The early 
stage was one of erosion. Most of what is now the United 
States was under water, and no small part of the material 
eroded was carried there from the north by rivers that 
formed a wide delta. Then came another upheaval greater 
than the Laurentian of the preceding era. This new system, 
called the Algomian, was followed by another vast period 
of erosion. Again a great mountain range was worn away 
to its very roots. This long process, aided by local sub- 
sidences and invasions of the sea, produced the so-called 
Huronian series, divided, as such systems generally are, into 
lower, middle and upper. 

The typical character of this great era is seen in the record 
of almost every feature known to geology. Thus it now 
appears that in the Huronian is embedded the evidence of 



74 OUR WORLD 

a glacial period, such as was formerly supposed to have 
occurred only at greatly later times. It is also in this sys- 
tem that the oldest fossils yet known are found — the secre- 
tions of certain algae, coral-like plant masses, comprising 
immense beds, repeated through thousands of feet. Besides 
these types, there are many traces of worm trails and bur- 
rows and the remains of other lowly orders. 

The Huronian was not followed by mountainous up- 
heavals. There were some undulations and warping, but no 
other great movements in this quarter until the present 
era. The term Algonkian has been very generally taken 
to include the entire Proterozoic; but eminent geologists 
now apply it only to the sub-era extending from the Hu- 
ronian to the close of the great era. In this sense, the 
initial series, the Animikian — the name being taken from 
the Animikie Indian tribe — is of much prac leal importance. 
It is made up of various deposits, usually of marine origin, 
and includes much of the iron-ore that now supplies in- 
dustrial enterprise in the region of the Great Lakes. Later 
came a great series of outpouring lavas, less the result of 
volcanic thrusts than of enormous and occasional discharges 
through fissures in the crust. These molten masses of the 
Keweenawan — from Keweenaw Point, Michigan — were of 
many kinds. Among the manifold rock formations there 
produced are the rich veins of copper, nickel and silver as 
well as lesser quantities of gold, platinum and other metals, 
exploited at the present day. 

The larger details of the Proterozoic are presented here 
because they indicate the chief processes of all later geologi- 
cal periods and thus afford a comprehensive idea of the 
physical history of the globe during the immensity of time 
through which the evolution of life has proceeded from 
obscure and simple origins. This sublime era is of course 
manifested on all existing continents; but nowhere is it 
seen in such grandeur as in North America. British Colum- 
bia, Montana, Idaho, Colorado, Arizona and the Adiron- 
dacks of New York expose huge remnants of its colossal 



THE GEOLOGIC RECORD 75 

formations. Its gigantic mountains, probably greater than 
the Alps, have been worn away, and their mighty stumps 
bear the varied burdens laid upon them in after times. 

The succeeding eras have long supplied the substance of 
geologic science. The vicissitudes through which the earth 
and its denizens have passed during this time have been 
the subject of such thorough investigation since Darwin's 
day that among men of science there prevails an entire 
agreement upon every essential feature. In the light of 
the phenomena that preceded, the successive scenes of this 
great drama may be sketched in rapid outline. 

THE PALEOZOIC ERA 

This drama of continents and life in evolution, compris- 
ing the sequel to pre-Cambrian time, is divided into three 
great eras ; the Paleozoic, the Mesozoic and the Cenozoic, 
words formed from the Greek, meaning ancient, middle 
and recent life. The former is divided into six periods, 
evidenced on all continents and everywhere characterized 
by geologists as the Cambrian, the Ordovician, the Silurian, 
the Devonian, the Carboniferous and the Permian. The 
introduction of these names gives some token of the begin- 
nings of geology as a science. The term Cambrian — the 
origin of which has already been stated — was introduced in 
1833 ; the Ordovician, also from a tribe of Wales in Roman 
times, was applied in 1879; the Silurian, from a tribe of 
ancient Britons, in 1835 ; the Devonian, from Devonshire 
in Southern England, in 1839; ^ ie Carboniferous, from its 
coal deposits, in 1821 ; and the Permian, from Perm, a 
Russian section near the Ural Mountains, in 1841. These 
periods are again subdivided into many lesser ones of local 
importance with local names. The limits of the six great 
periods of the Paleozoic have been shifted and defined with 
the progress of knowledge concerning them, while the lesser 
divisions have increased in number from time to time as the 
different formations have been more thoroughly studied. 



76 OUR WORLD 

These investigations are still conducted with zeal, and every 
year yields new facts to the sum of geologic science. 11 

The chief difficulty has always been in showing the cor- 
relation of the strata. Rocks of the same age may be of 
many kinds and in widely separated regions of the world, 
hence the precise periods to which they belong must be 
determined by means other than their composition. This 
process often presents difficulties requiring extraordinary 
technical skill, and like all other phases of science, compels 
correction and readjustment until the stage of positive as- 
surance is attained. One of the principal means of deter- 
mining the period to which any given formation belongs 
is the character of the organic remains within it. As these 
are abundant in all periods since the Proterozoic and clearly 
reflect the successive forms of plant and animal life, they 
become a reliable guide to the order of the changes through 
which the surface of the earth has passed. But this order 
is now so well established that the study of geology, as 
such, should no longer be burdened by the details of the 
variant forms of extinct life which fill so large a space 
in all works on the subject. These complex features be- 
long to biology in its largest sense, and even there the salient 
aspects of evolution would be more inviting and generally 
understood if they were less obscured by such a strange 
terminology and confusing myriad of unfamiliar species and 
varieties that the average student is appalled by the very 
sight of the printed page. 

During the Cambrian there were no violent and extensive 
crustal movements. The surface was not tossed and torn 
by volcanic convulsions. But in North America, which is 
regarded geologically as the typical continent, the gradual 
sinking and submergence of a large portion of the surface 
exposed at the beginning of the period is the distinguishing 
feature. It is apparent that a great lapse of time intervened 
after the last known formations of the preceding era and 
before this process began. There must have existed a 
long and progressive sequence of life between the sparse 



THE GEOLOGIC RECORD 77 

and simple forms of the Proterozoic and the profusion of 
the higher invertebrates revealed in the Cambrian. The 
absence of such series may be accounted for in part by the 
erosion and destruction of strata that contained the evidence, 
though it may be predicted with confidence that ample con- 
firmation will yet be found in systems which have been pre- 
served by submergence and covered by other sediments 
which have also escaped removal. 

At the beginning of the Paleozoic the areas above water 
were quite different in shape and location from those of the 
later eras. Nevertheless, great parts of the existing conti- 
nents were always exposed ; and they have tended progres- 
sively to gain their present form and stability. In other 
words, the great ocean beds have not radically changed, 
while the outlines of the continents have gradually been 
established by the elevation of the interior and the final 
adjustment of the continental platforms to the forces to 
which they have been subjected. To illustrate, in the lower 
Cambrian broad strips of territory, upon which mountain 
ranges along the Atlantic and Pacific coasts rested later, 
were depressed and through the hollows flowed the oceanic 
waters. A similar depression, at a later time the base of 
a mountain chain extending east and west and connecting 
the Pacific with the Gulf of Mexico, supplied another 
channel for the invading tide. Afterward the interior of 
the continent was flooded. These ups and downs continued 
until the end of the Mesozoic. The submergences varied 
in duration and area, but were always sufficient to accu- 
mulate sedimentary and limestone rocks thousands of feet 
in thickness and over a wide extent. When, therefore, it 
is stated that these overflows took place extensively nearly 
a score of times after the close of the Proterozoic, it will 
be seen how continents themselves are the products of an 
evolution requiring an almost inconceivable lapse of time 
for its accomplishment. 

From a purely geological point of view, the Ordovician 
was similar to the Cambrian in its main features, showing 



78 OUR WORLD 

the same uneasiness of the continental platforms, but no 
revolutionary activity, at least in North America. Not until 
the close of the period did any movements occur that caused 
great elevation. The Green Mountains of Vermont, the 
Berkshire Hills and the Highlands of the Hudson are rem- 
nants of the Taconic disturbance which then upreared a 
system of some magnitude extending as far south as Vir- 
ginia. Similar events took place on all the other continents ; 
the region now occupied in part by the British Islands was 
probably the scene of most violence. Limestones and shales 
are characteristic of the Ordovician. The resources then 
stored up have been of much service in the present age. 
Oil and gas have been tapped in great volume from the 
rocks of that period. These hydro-carbons (compounds 
of hydrogen and carbon) are of marine origin. They were 
produced by bacterial decomposition of organic matter. The 
particles of oil and gas disseminated through the rocks 
in which they were formed, were carried away by perco- 
lating water and finally collected into great cavities enclosed 
by impervious shales. Lead, zinc, manganese, marble, ce- 
ment, lime and lime phosphate are also obtained from the 
deposits of Ordovician time. 

The general characteristics of the Silurian are similar 
upon all the continents, so far as they have been studied. 
The period was somewhat shorter than the preceding ones 
of this era and records fewer changes. There was but one 
general submergence of North America, which occurred 
early; then after a long quiescence almost the entire con- 
tinent emerged from the waters. The great mass of rocks 
over which the Niagara pours its torrent was formed during 
this age of submergence. The seried strata piled high on 
either side of the gorge present a graphic record of the 
long process by which the sediments were built up, one 
after another. Through them the shelf of the Falls has 
slowly receded. In other localities a similar result, but 
from a different cause, is shown in the beds of rock-salt 
and gypsum. These two ingredients usually exist in sea- 



THE GEOLOGIC RECORD 79 

water in about equal degree. They are normally found 
together, if not afterward affected by the action of fresh 
water, where inland seas were left to evaporate when the 
elevation of the surrounding lands severed their connection 
with the ocean. There were considerable deposits of iron- 
ore along the Appalachian trough and elsewhere. The red 
fossil-ore (hematite) now utilized in the Birmingham dis- 
trict of Alabama belongs to this period. In many cities 
stately edifices of limestone and sandstone are modern mon- 
uments to the remote Silurian. As large sections of the 
nascent continents were long inundated and experienced but 
little volcanic disruption or discharge, the results in all such 
areas were similar to those in North America — extensive 
strata of sedimentary rocks as diversified as the materials 
from which they were derived. Lifted or lowered by sub- 
sequent movements, the Silurian deposits, for the most part, 
have either been stripped by erosion or buried under later 
accumulations. But wherever they are known they abound 
with proofs of the multiplying forms of life which then 
swarmed in the shallow waters of the submerged region 
where their fossilized remains are found. 

In its leading physical features the Devonian of North 
America resembles the preceding period. The same phe- 
nomena of rising and receding waters have left their record 
behind. The continent that emerged in the later Silurian 
continued through the early Devonian. Then followed sec- 
tional inundations increasing in extent until toward the close 
of the period, when again the continent became nearly in- 
tact. Volcanic action was far more vigorous and revolu- 
tionary in other parts of the globe, particularly in western 
Europe ; and it may well be that the rise and fall of the 
waters in North America were less due to the elevation 
and sinking of the surface than to changes in the sea-level. 
Obviously, if the oceanic beds were extensively raised by 
internal forces, the waters would rise to higher levels and 
overflow the lands lying below them. There is reason to 
suppose that such conditions developed many times in dif- 



80 OUR WORLD 

f ering degrees through geologic time ; and there is no reason 
to suppose that the crustal movements during the formative 
eras were confined to those parts which have become con- 
tinents. The islands of the South Pacific, as well as the 
maps of paleogeography, show changes in the floor of the 
oceans sufficient to alter the former strandlines by hundreds 
of feet. 

The most notable exhibit of the Devonian system in North 
America is in the Catskill Mountains, which resembles in its 
main features the famous Old Red Sandstone of Scotland. 12 
The important gas and oil fields of Pennsylvania, Ohio 
and West Virginia are also relics of this period. But its 
chief distinction is in marking an impressive stage in the 
evolution of life. The back-bone had at last been estab- 
lished, while lungs and brain had begun to bear their part 
in the scheme of nature. The phase of origins had passed, 
and the course of development had opened. Vegetation, 
which started at the water's edge, had become adapted to 
the soil and gradually spread its multiplying forms of ver- 
dure over the bleak and barren lands. The true primeval 
forests had begun to flourish and become the abode of the 
invading hosts that crawled out of the water to begin their 
devious career as the ancestors of the species that now 
inhabit the land. 

The Paleozoic era closed with the Carboniferous and the 
Permian periods. They were quite similar in general char- 
acter, though the latter is defined most clearly and exten- 
sively in Europe and Asia. It was in the upper Carbonif- 
erous that most of the great Coal Measures were formed. 
Before this phase opened, however, there was a succession 
of conditions such as prevailed alternately during the De- 
vonian. In North America this epoch is known as the Mis- 
sissippian. After the emergence of the continent during 
the later Devonian, inundation began once more, with its 
usual incidents, in the region of the Gulf and later spread 
over much of the Mississippi Valley, then through the 
western trough, styled the Cordilleran Sea, extending from 



THE GEOLOGIC RECORD 81 

the Arctic to the Pacific. After this deluge, the waters 
again retreated, leaving the low-lying exposed areas pecu- 
liarly suited to the coal producing agencies that now began 
their work. 

Long periods of luxuriant forest growth on low or 
swampy lands were followed by entire submergence, so 
that accumulations of woody matter were covered by strata 
of sediment. This arrested decay and permitted a gradual 
alteration of the substance. Under enormous pressure much 
of the oil and gas were forced out and the residue was 
slowly carbonized. As might be expected from the variety 
of circumstances in which they were produced, the coal 
seams differ in thickness and extent. In some localities 
the process was repeated many times. In many cases the 
overflow was fresh water; in others, salt. It is thus ap- 
parent that there were many movements of the underlying 
crust. Low country open to inroad by the sea was flooded 
through subsidence, while interior lands were covered by 
the waters of lakes and rivers impounded by the elevation 
of the channels through which the streams had previously 
flowed. 

During the remainder of the era the typical geological 
events of the preceding part recurred, but with increasing 
internal disturbances. In North America the upper Car- 
boniferous, here termed the Pennsylvanian, occurred another 
wide submergence, followed by a recession of the sea, which 
became complete in Permian time. The western section 
from California to the Polar Sea was marked by volcanic 
convulsions; and in the east broke out the Appalachian 
Revolution, the effects of which are seen to this day. The 
entire region from Newfoundland to Alabama was rent and 
contorted. The crustal unrest in that quarter during the 
Paleozoic culminated in a mighty cataclysm. The cause 
was not volcanic, but a gigantic lateral thrust that rumpled 
the horizontal strata into a mountain system, doubtless equal- 
ing in height and rugged grandeur any of the present age. 
The globe had been slowly contracting, and the surface 



82 OUR WORLD 

could only fit itself to the shrunken earth by folds and up- 
heavals where the push found weakest resistance. 

The geologic details of these periods on other continents 
present many diversities, yet the same essential character. 
The conditions that caused oceanic overflow and subsidence 
and finally the Appalachian uplift were present elsewhere 
and with similar results. Through central Europe and 
across the British Islands, as well as on every other con- 
tinent, are the remains of mountain ranges created by the 
same process of faulting, folding and upheaval. The con- 
solidation of the earth had reached another stage of re- 
adjustment by gravitation — a process by no means com- 
pleted, but at each stage promoting a more definite arrange- 
ment of its masses. In speaking of continents, it is not 
meant that their precise form was the same as now, but 
that they included all or the larger part of their present 
features. The excesses now lost were sometimes very con- 
siderable. For example, many geologists assume that at 
some time during the Permian and perhaps from the De- 
vonian, South America, Africa, India and Australia were 
joined by a prodigious stretch of territory that spanned 
the now intervening seas. The reason for this theory is 
solely the known distribution of certain forms of land and 
marine life assumed to have been impossible without the 
connection afforded by Gondwana, as this conjectured realm 
is styled. A situation the reverse of this is entirely certain. 
An ocean, called the Tethys, extended from western Eu- 
rope to the Pacific, overlapping southern Europe and north- 
ern Africa and passing through central Asia. Its expanse 
was variable. At times it connected with the Atlantic ; and 
through a depression between Europe and Asia it reached 
the Arctic Ocean. The Mediterranean, Black and Caspian 
seas are remnants of this shifting water-way that existed 
during several periods of the Paleozoic and later. Its 
changing lines are marked by the sediments it left and 
the fossil remains of the creatures that teemed in its waters 
along its shores. 



THE GEOLOGIC RECORD 83 

THE MESOZOIC ERA 

The Mesozoic, usually classed as the Age of Reptiles, 
though requiring millions of years for its strange and fas- 
cinating history, was not so long as the previous era; and 
its peculiar interest lies rather in the extraordinary evolu- 
tion of its life than in its geological features. Its ample 
records reveal no departures from the general method 
through which the earth has attained its present condition. 

Geologists have long divided this era into three periods : 
the Triassic, from the old-fashioned, but in most places 
inaccurate, three-ply denomination of its structure; the Ju- 
rassic, from the system as displayed in the Jura Mountains ; 
and the Cretaceous, from its broadcast and distinguishing 
chalk formations. 

The Triassic period was one of comparative quietude. 
Without extreme crustal movements, there were no new 
inundations of great sweep. In North America only small 
areas, chiefly coastal, contain sediments of this time. Else- 
where the general relation of land and sea remained much 
the same as at the close of the Permian. Volcanic action 
was here mostly confined to the northwest. It attained 
great violence in the Alaskan region and extended south- 
ward with diminishing force. In the east, igneous rocks 
of this period are scattered from Nova Scotia to North 
Carolina; but they were the peculiar sequel to the causes 
that produced the Appalachian uplift. The stress and strain 
had not been entirely relieved. New faulting and folding 
ensued. Thus were built up numerous lesser mountain 
chains, the vestiges of which still make many a landscape 
picturesque. The peculiarity of this movement was the 
outflow of molten matter through deep fissures in the dis- 
located crust. Great fractures yawned in many places 
throughout the area of disturbance, and from them volumes 
of basaltic lavas gushed forth. The most notable example 
of this phenomenon is seen in the Palisades of the Hudson. 

Over the greater part of North America the Jurassic 
was a period of erosion. The sediments of that time show 



"84 OUR WORLD 

a variable submergence of the regions near the Pacific 
coast; but later the Sierra Nevada range was formed in 
much the same manner as the ranges of the East had been, 
although accompanied by great intrusions of igneous rocks. 
The placer gold of California was the product of slate 
rocks laid down after these events; but the source of the 
deposits was concurrent with the gold-bearing quartz veins 
of the Sierras — fissures in the disrupted strata into which 
the molten magnas had welled up from below. Europe and 
Asia were extensively flooded during the Juassic. On the 
other continents the changes appear to have been similar 
to those in North America. 

The chalk deposits which very early gave its name to 
the Cretaceous were by no means general among the for- 
mations of that period. They are chiefly composed of the 
shells and skeletons of minute organisms, which have flour- 
ished from a very primitive stage in the development of 
life, but were especially abundant in some quarters during 
the Cretaceous. The most famous of these deposits are 
the Cliffs of Dover. 13 

The instability of many continental regions still con- 
tinued. The transgressions of the Tethys were the greatest 
in the history of the areas it affected. That part of the 
Gondwana between South America and Africa was now dis- 
rupted and sank beneath the wave. Twice during the period 
North America was invaded by the sea; though both in- 
vasions were in the south and west, where the flood had 
oscillated so many times before. The northeast was not 
subject to these inroads; but an extension beyond the pres- 
ent coast-line from Greenland to the Antilles now finally 
disappeared, leaving some marginal areas of shallow and 
variable submergence by the Atlantic and the Gulf of Mex- 
ico and extending well into the Mississippi basin. These 
conditions account for the numerous and important deposits 
of coal during this period. The petroleum of Texas, the 
sulphur of Louisiana and limestones of the west are also 
among its economic products. 



THE GEOLOGIC RECORD 85 

The period and the era closed with a series of geologic 
convulsions more severe on the North American continent 
than elsewhere. The greatest upheaval occurred in British 
Columbia. It was the beginning of the mighty easterly 
thrust that was eventually to create the mountain system 
extending from the Arctic Ocean to Cape Horn. In the 
northwest the movement was accompanied by enormous lava 
outflows never surpassed, except in India, where the Deccan 
lavas of the same epoch spread over 200,000 square miles, 
in some places more than a mile thick. During most of 
the Mesozoic the eastern part of the United States, except 
along the coast, erosion had reduced its rugged features to 
a peneplain, varied only in localities where the tougher rock 
masses resisted the wear and tear of the elements. When 
the era ended there had been another, but not violent, uplift 
along the Appalachian line, and a retreat of the sea from 
the coastal plain. This tilting of the surface furthered the 
work of rivers and streams, which have carved the charac- 
teristic features of the eastern landscapes. 

THE CENOZOIC ERA 

The geology of the Cenozoic, the Age of Mammals, may 
be sketched in broader outline. The era is divided into the 
Tertiary and the Quaternary periods, though both terms 
have become misnomers through advancing knowledge of the 
pre-Cambrian. They are so embedded, however, in the lit- 
erature of science that they persist despite their inaccuracy. 
The Tertiary is subdivided into four epochs, Eocene, Oli- 
gocene, Miocene and Pliocene, derived from the Greek and 
marking gradations of the word "recent." Thus, in the 
order given, they signify dawn of the recent, little, less and 
more recent time. 

The Tertiary accomplished the entire and final emergence 
of North America from the waters. The elevation of the 
interior had already drained the inland seas. There were 
some marginal overlaps along the Atlantic and Pacific coasts. 
These shifted back and forth, but gradually lessened until 



86 OUR WORLD 

the present shore line became fixed. The greatest sub- 
mergence was in the Gulf States and the Mississippi 
valley. Late in the Oligocene a portion of Florida was an 
island. Not until the late Pliocene did it become as now 
a peninsula. Its rise was concurrent with that of the Mis- 
sissippi basin, which reduced the Gulf to its present general 
outline, with some marginal variations, until into the pres- 
ent era. 

Several times before the Tertiary North and South Amer- 
ica had been severed, as shown not only by the sediments 
deposited in the region of the Isthmus, but also by the sharp 
breaks in the spread of animal life. In the Cretaceous this 
chasm was again bridged, only to be broken during the 
Eocene. Not until Miocene time was the union finally re- 
stored. Intermittently through these long ages volcanic vio- 
lence reigned along the Pacific coast. It attained its greatest 
intensity during the Miocene and continued into the Plio- 
cene. From Southern Mexico to Alaska at least eleven 
powerful volcanic centers were scattered. Mount Rainier, 
Mount Shasta and Lassen's Peak in the Pacific states, Popo- 
catapetl, Ixaccihuatl and Orizaba in Mexico continued their 
activity long after the Tertiary closed. Indeed, the smoke 
and fumes of some of them at the present day are a portent 
of danger. The troubled career of the West Indies likewise 
culminated in volcanic upheaval, and in South America like 
phenomena became pronounced. The Andes then began 
their gigantic ascent. During the Pliocene the Rocky 
Mountains, which had previously begun to rise, were pushed 
upward thousands of feet. In other words, the mighty 
eastward thrust, which began in the late Mesozoic, was 
renewed with added force along the entire Pacific coast 
of both Americas, though the results of greatest magnitude 
as yet were in the north. Then originated the great San 
Francisco fracture, the immediate cause of many earth- 
quakes which have shaken that region. The catastrophe of 
1906 was the result of a slip along that rift, which is a 
continuing menace to the stability of the adjacent country. 



THE GEOLOGIC RECORD 87 

The Yellowstone Park was a product of Miocene volcanoes. 
In the basin of the Columbia many thousand square miles 
were covered by lava flows. During the Pliocene, and per- 
haps somewhat later, the plateau of the Colorado was lifted 
several thousand feet ; and through that rock-bound mass the 
river has since carved out the Grand Canon to a maximum 
depth of nearly a mile and a half — the most extraordinary 
geologic exposure on the globe. 

The cause of these colossal movements was the renewal 
of the stresses so vigorously shown in the later Mesozoic; 
hence they were not confined to the Western hemisphere. 
In the Oligocene the Rif Mountains of Morocco, the 
Pyrenees of Spain, the Appenines of Italy and the Car- 
pathians of the Balkan Peninsula began to rise. They were 
followed in the early Miocene by the rise of the entire 
Alpine system, which reached its full proportions in the 
Pliocene. As usual in the formation of mountain systems, 
the Alps were produced mainly by folding. The thrust was 
from the southland its force was felt as far north as the 
London basin. Thus the snow-clad summit of the Matter- 
horn was pushed bodily from a great distance to rest upon 
an entirely alien base. It was in the Pliocene that the vol- 
canic districts of the Mediterranean region became active. 
Vesuvius and i£tna then began their fitful eruptions, so dis- 
astrous in historic times. 

In southern Asia similar phenomena were repeated on a 
grand scale. During most of the Eocene the whole region 
was undisturbed, though flooded to a greater extent than 
ever before. Then the contraction of the Tethys set in 
through the process of faulting and folding. Northern India 
and Burma emerged from the waters and assumed a moun- 
tainous aspect. In the Miocene the movement was renewed, 
lifting the mountains higher and breaking up the Tethys 
into disconnected basins, of which the Mediterranean is the 
most important in modern geography. The climax came in 
the Pliocene, when the majestic Himalayas were raised to 
the clouds. The stupendous thrust and upheaval that at- 



88 OUR WORLD 

tended it affected the regions to the north as far as Thibet 
and Mongolia. 

The ragged coast-line of eastern Asia, with its extensive 
fringe of islands, large and small, would alone suggest the 
vicissitudes through which that part of the continent has 
passed. The adjacent waters are mostly shallow, so that the 
variations of the sea-level, from whatever cause, would work 
corresponding changes in the shores of the mainland. Al- 
though the changes have not been studied as thoroughly as 
in other quarters of the world, enough is known to indicate 
many and important variations. During the Tertiary the 
last remnants of the Gondwana sank into the oceanic beds. 
On the other hand, the reach of water between the Arctic 
and the Tethys at last closed up. The rise of the Caucasus 
Mountains, the steppes of Russia and the long sag west of 
the Urals joined Europe and Asia as a continuous mass. 



THE ICE AGE 

As in many other instances of geologic sequence, the line 
of division between the Tertiary and the Quaternary is 
obscure, because the transition was gradual in those regions 
not radically affected by the climatic changes that followed. 
The tumult of the Pliocene slowly subsided and the condi- 
tions that were eventually to render the Pleistocene (most 
recent) perhaps the most remarkable period in geologic 
history become apparent. From a warm and salubrious 
climate, a large part of the temperate zone of North Amer- 
ica, Europe and portions of Asia were covered with ice. In 
America the ice sheet extended southerly along an uneven 
line just below the Canadian border to the Missouri, thence 
along that river and the Ohio and still eastwardly at about 
the latitude of Long Island. In Europe it enveloped most 
of Great Britain and extended thence along an irregular line 
into Asia. That the conditions which produced this glacia- 
tion were general is shown by the fact that not only both 
polar zones and all regions of high altitude were affected, 



THE GEOLOGIC RECORD 89 

but also those parts of South America and Australia lying 
in latitudes corresponding to those of the frozen north. 

In its details the Pleistocene of North America has not 
been as thoroughly elucidated as that of Europe ; but enough 
is known of its main features to afford a clear idea of what 
took place. Thus the ice made several general advances and 
probably others of lesser extent. Inasmuch as life was ex- 
tinguished under masses of ice several thousand feet in 
thickness, similar to the glaciers at the present time on the 
shores of Greenland and Antarctica, there are few fossils 
to gauge the occurrence. The denizens of the Arctic were 
pioneers of the ice. Walrus disported on the strand of New 
Jersey; the musk-ox foraged in Oklahoma; and the wooly 
rhinoceros, on the banks of the Potomac. The existence of 
these vast mantles of ice is shown by the debris they left 
and the changes they wrought in the areas they covered or 
affected. When they melted and the regions again became 
suited to life, it again reappeared from the warmer parts to 
which it had retreated and again gives its testimony where 
it has not been worn or washed away. Since the evidence of 
glaciation is always the same, it is often difficult or impos- 
sible to separate one glacial stage from another, especially 
where the products of the intervening time have been re- 
moved. It is known, however, that the main inter-glacial 
periods were much longer than the glacial and also much 
warmer than the same latitudes are now. The various char- 
acter of the Pleistocene may be inferred from its outstand- 
ing events and its probable duration. The time that elapsed 
from the advance of the first ice sheet to retirement of the 
last is estimated at not less than 400,000 years and may have 
been a million more. 

The Glacial Age presents one of the most difficult prob- 
lems of geologic science, and the authorities are not yet in 
agreement as to the cause or causes of it. Interest in the 
question, however, is unabated, and it is furthered by the 
fact that the Pleistocene, glacial and inter-glacial, includes 
the early history of the human race. Moreover, many 



90 OUR WORLD 

natural features of the earth's surface as they now exist are 
due either to movements of the ice-sheets or the torrential 
effects of their melting masses. 

There were two periods of glaciation, more or less im- 
portant, in the pre-Cambrian. Another occurred in the 
Permian nearly as extensive as those in the Pleistocene, 
though more marked in the southern hemisphere; other- 
wise its chief characteristics were very similar to the 
phenomena of the later time and were doubtless produced 
by similar causes. 

It is assumed that the ice sheets resulted from conditions 
similar to those which now r produce glaciers. Their en- 
croachment, however, upon the temperate zones and upon 
areas much less elevated than those upon which glaciers in 
those zones are now formed indicates a general temperature 
lower than in the present age. Thus it is calculated that the 
snow-line descended about 4,000 feet, which might have 
been caused by a drop of some ten degrees in the average 
heat from the sun. Glaciers are formed by accumulated 
snowfall ; hence they not only require immense and long con- 
tinued precipitation, but continuous cold, which can only be 
found in altitudes above the snow-line. But altitude alone 
does not cause precipitation. There must be currents to 
carry a moisture-laden atmosphere; and these in turn are 
guided by the conformation of the surface over which they 
pass. The tremendous changes in the topography of the 
continents after the upheavals in the Tertiary must there- 
fore have been a contributing cause. Likewise the ocean 
currents are an important agent in climatic conditions ; and 
these currents may have been radically affected by changes 
in the ocean floors, shores, and channels produced in the 
same period and in the same way as the changes on land. 

It is obvious that immense evaporation from the oceans 
and the bodies of water inland, which were so great and 
numerous in the Tertiary that it has been called the Age of 
Lakes, must have occurred to supply the ice covering many 
millions of square miles to a thickness of from 4,000 to 



THE GEOLOGIC RECORD 91 

10,000 feet. And such was the fact. It is known that the 
sea-level was lowered from 200 to 300 feet. Theories that 
climates may have been altered by changes in the orbit of 
the earth and the tilt of its axis have found no encourage- 
ment from astronomy ; nor do geologists see any indication 
whatever of changes in the tilt, if such changes would have 
wrenched and deformed the crust. However, the argument 
is still advanced that gradual oscillations of the axis would 
be caused by tidal action and that when the axis was per- 
pendicular to the ecliptic, during widely separated periods, 
seasons and differential climates would disappear. The 
probable variation in the amount of carbon dioxide in the at- 
mosphere at different periods, lessening the retention of the 
sun's heat, has also been suggested as a cause. While in 
some cases this may have been one of the features, it leaves 
other concurrent phases unexplained and is therefore to be 
regarded rather as an ingenious speculation than a final 
solution. That an extraordinary amount of volcanic ash in 
the atmosphere, according to another theory, could lower the 
effective heat of the sun for ages at a time is quite improb- 
able. From the evidence now available it would seem most 
likely that the sun has been the main cause of the glacial 
periods ; and this conclusion is supported by the inter-glacial 
times, which might have been very natural results of in- 
creased radiation after intervals of obstruction. 

The cumulative effects of the Pleistocene were so great 
that, after the lapse of from 20,000 to 50,000 years (the 
estimates vary) since the last glaciation, they yet retain 
their extraordinary features. Besides the normal move- 
ments of the crust continued from the turbulent Tertiary, 
there were extensive warpings caused by the weight of the 
ice. But the distinguishing effects of the ice-sheets were due 
to the advance of the glaciers and the force of the water 
discharged by melting. These effects would seem incredible 
were not the evidence so impressive. 

The glaciers were thrust forward by additions in the rear, 
in the same manner as the glaciers of to-day, though on a 



92 OUR WORLD 

vastly greater scale. The lobes were of many widths, from a 
few miles to hundreds. As the sources of dispersion were 
mountainous regions, ponderous masses of rock were caught 
in the advancing sheets and thus pushed or dragged over the 
surface below, in many cases for hundreds of miles. This 
process, continued for ages, scored and ploughed the path- 
ways of the movement. Rocks were broken and ground into 
all manner of debris, ranging from huge boulders to till 
and clay, forming the moraines that mark the glacial ex- 
tremes. 

The ice-sheets that centered in Labrador were finally dis- 
persed through the St. Lawrence basin and the regions to 
the south. All the mountain systems of New England and 
New York, except the Catskills, were wholly buried in the 
ice. The record is graven on the rocks and the watersheds. 
The Adirondacks divided the movement in that quarter. 
One lobe thrust its way through the Champlain valley, and 
its departing waters passed through the Hudson. Another 
scoured out the beds of the Ontario and the chain of pic- 
turesque lakes in central New York, all much larger than 
now. Their turbid overflow found the devious channels of 
the Mohawk and the Susquehanna. 

In the west a similar history is unfolded. The Great 
Lakes, variable and vaster in their original spread, are the 
work of the glacial epoch. A body of water greater than all 
these lakes combined came from the dissolution of the 
Keewatin ice-sheets, which centered in the far north. It 
flooded the plains of Manitoba, Montana and the Dakotas, 
now one of the chief graneries of the world. The flow of 
water from these vast sources developed the master drain- 
age systems of the country. The Missouri and the Ohio 
were thus given their present courses. The Mississippi was 
a mighty stream from the place where it tapped the deluge 
of the north. As the ice retreated the flood abated. The old 
river systems had been filled with drift and changed to con- 
form to a new topography. The Great Lakes were gradu- 
ally reduced to their present dimensions, and their outlet 



THE GEOLOGIC RECORD 93 

established through the St. Lawrence. Lake Champlain and 
Lake George were the deeper parts of an inland sea con- 
necting with the Atlantic through the Canadian basin; 
marine shells and the bones of seals and whales have been 
found far above the present water-level. 

These familiar features of American geography are the 
most notable relics of the Ice Age; yet they are typical of 
the results produced in every region that was affected by the 
torrents discharged from the melting glaciers. Innumerable 
lakes that still dot the landscape with their picturesque 
waters had their origin in these floods, while many others 
have vanished, leaving their alluvial beds to fruitful tillage. 
Only those remain where the rainfall along their tributaries 
makes good the loss through evaporation. 

It is a fact of profound significance in estimating the 
factor of time in geologic history that, notwithstanding the 
many thousands of years since the close of the Ice Age, of 
which the recorded annals of the human race are but a frac- 
tion, the characteristic lineaments of the globe have under- 
gone no material changes. During the late Pleistocene, 
however, there w r ere many readjustments. The continental 
elevations during that epoch were followed at the close by 
general and local subsidence. Land areas and connections 
had shut off warm ocean currents, thus serving to lower the 
temperature. The opening of channels, old and new, must 
have contributed to milder climates. It was then that Hud- 
son's Bay was formed, and the Behring Sea and Straits 
broke the union between Alaska and Siberia. The land con- 
nection between Ireland and Britain sank into the Irish 
Sea ; and that between England and the continent, into the 
North Sea and the Channel. The Baltic Sea poured into a 
similar depression. Throughout the Mediterranean changes 
took place. The Strait of Gibralter opened. Between Italy 
and Africa the land bridge subsided, leaving Sicily the sur- 
viving remnant. Malta became an island. Between Greece 
and Asia Minor the land gave way to the yEgean Sea ; and 
the Black, Caspian and Aral Seas sank to their present level 



94 OUR WORLD 

Java, Sumatra and the East Indian Islands were severed 
from the Malayan Peninsula ; and probably Japan from the 
Philippines. New Guinea and Tasmania were likewise sep- 
arated from Australia. The modern world had taken the 
form we know. The present configuration of the lands of 
the earth and the climates that invest them are still in their 
youth. What terrestial revolutions the future may bring, 
one man may guess as well as another. That they will come 
cannot be doubted. 

THE AGE OF THE EARTH 

It is obvious from any resume of the geologic periods 
through which the earth has passed that time has been the 
decisive factor. Expressions of magnitude and the marvel- 
ous as descriptive of things within common experience are 
but feebly suggestive of what has been accomplished by 
elemental matter on the scale of worlds and astronomic sys- 
tems. Not less difficult to adjust to comprehension is the 
lapse of time required by nature's evolutions. To the con- 
templative mind the vistas of the past are oppressive. 

Before science revealed the antiquity of the globe and 
the long processes in the evolution of life, it was convenient 
to regard the earth as created out of nothing in the twinkling 
of an eye, and the successive orders of life by separate acts 
of creation. When at length the truth began to dawn, the 
problem of time became urgent; and few problems have 
been attacked with more ingenuity and greater resources, 
though with inconclusive results. The best solution is as yet 
only a rude estimate ; but it is amply sufficient to satisfy the 
demand of theory. 

The most usual method of computation has been to meas- 
ure the amount of sedimentation by the average rate ob- 
tained through observation of river deltas. This rate, how- 
ever, supplies an uncertain standard, because the deposits 
of the different rivers vary enormously, owing to the diverse 
nature and volume of the materials and the force of the cur- 
rents. The obverse method is to ascertain the rate of erosion 



THE GEOLOGIC RECORD 95 

from observed localities and from it calculate the time for 
the known extent, as, for example, the gorge below Niagara 
Falls. The advance and retreat of glaciers has aided in com- 
puting the duration of the Ice Age. The Coal Measures and 
the vast deposits of limestone in every geologic period have 
also afforded reliable data. Another method of calculation, 
which is regarded with much confidence, is the salinity of 
the oceans, assumed to have come from the exposed lands. 
The results thus obtained accord very well with those at- 
tained by other means. A few years ago a precise calcula- 
tion was expected through the radium content of certain 
rocks; but more advanced knowledge of radioactivity has 
rendered this method of doubtful value. Nevertheless, it 
must be that the x of this problem will eventually be found. 
All the other factors are present. The earth in all the var- 
iety of its outer formations is known, and the evolution of 
life is certain. Neither the earth nor life as they now exist 
would be possible without the lapse of sufficient time. 

The leading authorities assume the lapse of at least 80,- 
000,000 years since the beginning of the sedimentary rocks 
of the Archeozoic — an adequate time for organic evolution. 
Probably the great majority of geologists would adopt a 
much higher estimate, and some would increase it many 
fold. Certainly no reasoning mind can question the vastness 
and plenitude of time as a factor in the history of the earth. 



CHAPTER IV 
WAYS AND MEANS 

WATER 

SCIENCE is always confronted with the tangible. Specu- 
lation is therefore restrained by unyielding realities. If 
the efforts to explain are not conclusive, they must persist 
until theories merge into facts. 

The special sciences are but systems of related phases. 
They begin with assumption of the fundamentals and end 
with concrete results; and the results so accomplished are 
attested by the progress of positive knowledge and the mani- 
fold achievements in the industries and the arts. Techni- 
cians eagerly await announcements by the great seekers for 
principles, and the by-products of their researches are turned 
to account in the factory, the mill and the market-place. 

To one wholly unversed in the principles of physics and 
chemistry the components of this world of ours, familiar as 
many of them are, present puzzles most intricate and ob- 
scure. The literature of chemistry (with its appalling 
terminology of various origins, and its multifarious laws, 
often named after their discoverers) is in an alien tongue, 
and its ideas are as those of another sphere. However, it 
is some comfort to know that most of this enormous lore is 
useful only to the technician and the historian of opinion. 

Physical chemistry, though the youngest of the greater 
sciences in designation, is the oldest in its sources. Interest 
A in matter, the materials of existence, was necessarily 
aroused at the earliest dawn of intelligence and has steadily 
increased at every stage of mental development. As knowl- 
edge of foods, clothing, weapons, ornaments and medicines 
extended, civilization progressed. This result was attained 
precisely in proportion as mind reacted upon matter and 

96 



WAYS AND MEANS 97 

brought it into service. During the thousands of years that 
elapsed from the practical beginning of chemistry to the 
opening of the nineteenth century the underlying principles 
were scarcely exposed. 

It is not surprising that the ancients regarded water as 
the basis of life. If among essentials one thing can be more 
important than another, water is the principal operative 
factor in the conditions of our world. Yet it is a striking 
commentary on the slow progress of scientific chemistry 
until modern times that not until well within the eighteenth 
century was oxygen isolated and then found to be a con- 
stituent of the atmosphere. Then followed the discovery 
that water is composed of two gases, oxygen and hydrogen. 
Necessarily it was not until this period that the phenomena 
of combustion began to be understood. 

From the human point of view, water is the great mir- 
acle of nature. First in importance is the fact that its proper- 
ties are effective within the same limits that bound the ex- 
istence of life. It is the greatest of all solvents and there- 
fore the cause of most of the chemical reactions essential 
to life. The reasons for this were not apparent until long 
after the true nature of water became known, when the pro- 
gress of electrical research began to explain the constitution 
of matter. Of the more common liquids, water has the 
highest dieletric constant. It contains the largest number 
of simplest chemical molecules. It possesses the two most 
important and the swiftest ions — one producing all the acids 
and the other all the bases. These energies give water its 
great solvent power. It dissociates many of the compounds 
with which it comes in contact and is the chief agent in 
causing new arrangements according to the elements in- 
volved. Thus originate, for the most part, the complex com- 
binations — new substances — required in the production and 
maintenance of organic structures, as well as the chief trans- 
formations of the earth's surface. 

The permanence of water is another characteristic that 
renders it so important in the scheme of things. No com- 



98 OUR WORLD 

pound is more enduring through the varied conditions to 
which it may be subjected. Whether as ice or liquid or 
steam or highly heated vapor, its essence remains unchanged 
and the bonds of its union unrelaxed. Whatever may be its 
present relations with other substances and combinations, 
it has retained its true character in countless others through 
the course of time ; for during geologic time, the volume of 
water has remained practically constant and has ever been 
marvellously adjusted to the needs of the earth as an abode 
of life. 

Another of its peculiar properties, and one possessed by 
few other liquids, is that though it contracts until the tem- 
perature lowers to 4 degrees centigrade, it then expands until 
it reaches the freezing point. It is for this reason that ice 
floats. If it contracted it would become heavier than the 
liquid and sink. The greater bodies of water would rapidly 
accumulate ice that the most torrid summers could not 
melt. Life in the oceans, seas and lakes, would have been 
impossible and doubtless the effect on the atmosphere would 
have glaciated the continents and prevented geological 
changes that are normal under the conditions that prevail. 

The chemical nature of some of these transformations 
should be clearly understood because of their great import- 
ance and the immense scale on which they are wrought. In 
addition to water the prime factors in these processes are 
oxygen and carbon, the latter being effective in conjunction 
with oxygen as carbonic acid gas — carbon dioxide. To illus- 
trate the complex preparation of primal matter for organic 
uses, both as a habitat and as materials for the chemistry of 
life, take the case of an extensive mass of volcanic lava 
ejected from the interior of the earth where its changes 
were more physical than chemical. In the molten state it 
was solvent; the original components were fused and 
blended more or less completely. As soon as it was ex- 
posed at the surface chemical action began. Greedily at- 
tacked by oxygen, which of all the elements unites most 
freely with the others, the simpler substances were con- 



WAYS AND MEANS 99 

verted into higher ones by oxidation. Water promptly lent 
its efficient aid and yet other combinations were produced. 
Much of the matter that was still able to resist these reac- 
tions yielded when carbon dioxide joined the assault. This 
matter was thus brought into solution and then built up into 
carbonates suitable for organic assimilation. 

The greater part of the rocks forming the continental 
masses is composed of feldspar containing silicates of 
alumina with lime, soda or potash. Under the reaction of 
aqueous solutions the potash is removed and converted into 
soluble forms that freely enter into vegetable growth, and 
upon the vegetable products animals directly or indirectly 
subsist. When organisms die and decay the same materials 
are again in condition to renew the organic cycle. 

One of the most important geologic features is the result 
of this process of disintegration and solution followed by 
organic consumption of the lime so dissolved. The carbonic 
acid gas was originally exhaled for the most part by vol- 
canic means; and very probably the atnfosphere contained 
much more than at present. Natural surface water acquired 
more or less of this gas in solution. Some is gathered by the 
rainfall in its passage through the air and some during its 
percolation through the rocks and soil and much is supplied 
by decaying vegetation. Many of the products of such solu- 
tions are ultimately drained into the seas, where the lime- 
stone rocks, which exist in great profusion and variety, have 
been formed from remote geologic time. They are composed 
mainly of carbonate of lime, forming the mineral known as 
calcite. The lime in the original drainage is usually in the 
more soluble form of bicarbonates, which is therefore more 
readily assimilated. These are reconverted into carbonates 
by myriads of minute organisms whose remains are readily 
distinguished in the rocks they have created. The dolomite 
rocks, which are much harder, are limestones into which 
carbonate of magnesium has afterward been infiltrated. 

The immense geological effect of the solvent action of 
water and carbonic acid is furthered by the composition of 



100 OUR WORLD 

another type of secondary rocks. Granite contains various 
combinations of quartz and feldspar. When decomposed, 
the feldspar, in a finely divided state, becomes clay ; and the 
particles of quartz become sand. When masses of sand 
were so situated that they were impregnated with solutions 
of carbonate of lime or magnesium or both under the weight 
of other geologic strata they were cemented together thus 
forming the sandstones. 

It is apparant, then, that the soils are the product of 
chemical action mainly. The raw materials are chiefly sand 
and clay, which of course exist in great abundance and 
variety. They are the first results of the decomposition of 
the rocks. Loam is merely a mixture of sand and clay. Marl 
owes its character to the carbonate of lime it contains. Muck 
is a mixture of earths rich in humus, which is mainly car- 
bonaceous material from decaying vegetation. From these 
simple facts it is obvious that what is known as agricultural 
chemistry has a very real basis and a very great utility in 
determining the resources of the soils, their availability for 
tillage and the treatment they require to promote their 
fertility. 

These examples are given to illustrate the more conspicu- 
ous results of the greater chemical reactions which have 
made the earth a habitable planet. Starting with a hetero- 
geneous crust, vast areas of crude elemental matter in all 
manner of sheer physical confusion originating in the molten 
flux, the cooled masses have been brought by natural chem- 
istry into the diversified condition that now exists. 

THE LAWS OF MATTER 

There is no explanation as yet of the relative proportion 
of the elements as they exist in the known world. Oxygen 
is by far the most abundant, being estimated at very nearly 
50 per cent, of the total. It comprises most of the atmos- 
phere and also exists free to the extent of about 23 per cent. 
by weight. In pure sand and clay and many silicious rocks 
it constitutes about 53 per cent.; in limestone, about 48 per 



WAYS AND MEANS 101 

cent. ; and in other materials it is present in a similar 
degree. 

The next most abundant element is silicon, which in nature 
is always combined with oxygen. It amounts to about 26 
per cent. Hydrogen constitutes about 1 per cent, and carbon 
about y 5 of 1 per cent. The other elements exist only in 
relatively small quantities. Hydrogen is almost entirely in 
combination ; hence it has been suggested that if the amount 
were 10 per cent, greater its combination with the existing 
free oxygen would have formed water enough to submerge 
most of the continental areas. Yet this peculiar adjustment 
is not more striking than the volume of the atmosphere. If 
it were one-half of w T hat it is glaciation would have begun 
long before it did and be unceasing. 

What are these elements that so indifferently, according 
to the conditions, compose suns, planets and living things? 
This is and always has been the master question of science. 
The ingenious Greeks conceived of matter as made up of 
ultimate particles, which they called atoms, probably bor- 
rowing the idea from the more ancient Hindus. But, as with 
most other generalizations of that period, this was merely a 
guess. The Greeks were much more keen in speculation and 
argument than in physical demonstration. In this loose form 
the idea long persisted without further development. It was 
not until chemistry began to assume a scientific character 
that the atomic theory took a definite form and became an 
efficient medium of chemical practice. Announced by Dalton 
in 1803, it soon gained general acceptance because it worked ; 
and for nearly a century the atom, though hypothetical, was 
regarded as the very real and irreducible minimum of the 
element to which it belongs. 

No other hypothesis ever devised has been so fruitful of 
practical results. In this respect it has even surpassed the 
theory of the ether, as imporant as that has been in discov- 
ering the laws of radiation. The science of chemistry has 
been chiefly due to the application of the atomic theory ; and 
whatever may befall the theory as such, it will continue as 



102 OUR WORLD 

the practical basis of applied chemistry in all its branches. 
This is because of the fact that the unit of the atom holds 
good as the proximate constituent of matter, whatever may- 
be its ultimate nature and composition. 

The atomic theory assumes that each element is composed 
of ultimate particles precisely alike and indivisible. From 
this logically follow the fundamental laws of chemistry. If 
the atoms are indivisible they are indestructible; hence the 
law known as conservation of mass. The atoms of each ele- 
ment being alike and indestructible, a pure compound always 
contains the same elements in a constant ratio by weight; 
hence the law of definite proportions. For like reasons, 
whenever more than one compound is formed from the 
same factors and one of them is fixed in amount, the quan- 
tities of the others in the different compounds vary in 
simple ratio ; hence the law of multiple proportions. Inas- 
much as chemical changes involve the addition or subtrac- 
tion of atoms or molecules — that is, elements or compounds 
— the differences are found by computation based on 
weights. The relative amounts of elements which combine 
with a fixed amount of oxygen are also equivalent when they 
combine with other elements. This law is known as that of 
reciprocal proportions. But the principle of greatest prac- 
tical importance is that of combining weights. The com- 
pounds of pure chemical compounds may be accurately ex- 
pressed in terms of fixed numbers, or multiples of them by 
integers, each element having its own combining weight. The 
equivalent weights represent the weights of the elements in 
combination with oxygen fixed at 8, while the atomic weights 
are based on oxygen at 16, for practical convenience. 

These laws obviously take substances into account only 
according to their respective weights ; and as the various 
elements all have different weights, it has been necessary in 
exact chemistry to know them with as nearly absolute pre- 
cision as possible. This has required the utmost nicety of de- 
termination. The weights have been repeatedly redetermined 
and the corrected list standardized the world over. Yet the 



WAYS AND MEANS 103 

table i§ evef subject to revision and will be until substantial 
error is removed, though absolute precision on this basis 
may be impossible. 

If the science of chemistry had depended wholly upon 
knowledge derived from the study of solid substances, but 
slight progress would have been made. From a technical 
point of view, little is known about the internal mechanism 
of matter in a solid state. The geometrical forms in which 
it crystalizes are known and also something about the way 
in which solids conduct different forms of energy — light, 
heat and electricity; but the molecular weights of the sim- 
plest solids are unknown. There are no reliable means at 
present of finding out the formula of such a common thing 
as rock-salt or ice. 14 

It was seen very early that in every chemical reaction heat 
is produced or absorbed, and that light or electricity may 
also be produced according to the conditions. This showed 
that in every such reaction there are two kinds of changes — 
of matter and of energy. Naturally the material changes were 
first studied, because they were the most obvious ; and both 
kinds of changes are most readily revealed in solutions. 
Thus at the present day the major part of chemical inves- 
tigation is carried on by means of solutions. This indeed is 
the great medium of nature. Not only are solutions the 
chief vehicles of geologic change, but of the organic pro- 
cesses as well. 

Yet it was not solutions that gave direction to the modern 
trend of chemical theory. This factor was gas. As any gas 
when confined exerts a pressure, the explanation was eagerly 
sought; if found, it would manifestly lead toward explana- 
tion of the nature of matter itself. It was long supposed 
that some gases are not capable of being changed into 
liquid or solid form; but the fact was finally demonstrated 
that every gas, under suitable conditions, can be liquified. 
When it was found that hydrogen, the lightest of all known 
elements, is present in a great diversity of solid combina- 
tions, and that all solids can become gaseous, the conclusion 



104 OUR WORLD 

was inevitable that there are no essential differences in 
matter of whatever kind. 

The analogy between gas and other phases of matter is 
apparent from the laws of their behavior. Every gas has its 
own degree of pressure, which never varies under like con- 
ditions and is proportionally affected by the compression 
and temperature to which it is subjected. Even before he 
announced the atomic theory, Dalton had discovered that 
in any mixture of gases which do not combine chemically 
each gas exerts the same pressure as if it were alone, and 
that the total pressure is the precise sum of the separate 
pressures. Nor is this property affected by the mixture of 
gases with liquids. When a gas is dissolved in water, the 
quantity that can be dissolved varies with the pressure 
of the gas ; and with a mixture of gases so dissolved, each 
gas acts independently of the others. Quite significant of 
the quality of motion necessary to such phenomena is the 
equally positive law that the volume of a gas varies in- 
versely with the pressure. 

In 1811, Avogadro, an Italian physicist, announced the 
law that equal volumes of all gases, under like conditions of 
temperature and pressure, contain approximately equal num- 
bers of molecules. A molecule is the smallest mass of an 
element or a compound which can exist by itself. The 
weights of gaseous molecules are directly proportional to 
the specific density of the gases, and from the known density 
of the elementary gases it follows that many of them consist 
of molecules of more than one atom. A large proportion of 
the molecules move in groups which become smaller with 
increase of temperature. Thus a molecule of water in the 
state of gas consists of two atoms of hydrogen and one of 
oxygen. As liquid at the ordinary temperature of the air 
the molecules join or move together in combination of two 
or more. The law of Avogadro has been the most important 
means of correlating chemical facts and is thus fundamental 
in practical chemistry. Yet it was not until about i860 that 
the principle was generally accepted, because a clear distinc- 



WAYS AND MEANS 105 

tion had not been drawn between the molecule and the atom 
as the physical unit of matter. 

The property of motion possessed by all atoms in a 
gaseous or liquid state is further illustrated by one of the 
most important of organic processes. This is known as 
osmotic pressure (from osmosis, Greek for "a push"). 
Growth is made possible by means of appropriate materials 
being taken from the environment in a gaseous or liquid 
condition. The necessary matter in solution is taken into 
the system, animal or vegetable, by means of membranes 
which are permeable only by the substances required by the 
organism, the others being normally excluded. The circu- 
lation of the blood, including all the phenomena of breath- 
ing, is the most notable example of this process. The di- 
versity of function shown by the membranes is one of the 
wonders of nature ; yet the process itself is simple in prin- 
ciple. Thus it is readily available in chemical work and is 
accordingly employed to separate certain ingredients in solu- 
tion. The action proceeds according to laws analogous to 
the diffusion of gases. 

The osmotic pressure varies directly as the concentration, 
and the pressure of a solution of uniform strength increases 
proportionally with the temperature. Moreover, the osmotic 
pressure of any substance in solution is the same as it would 
be if present as a gas in the same volume as that occupied by 
the solution, provided the solution is quite dilute. Solutes 
(the substances dissolved) when present in the ratio of their 
molecular weights in equal volumes of the same solvent ex- 
ert the same osmotic pressures. These laws may appear 
somewhat technical, but they are quite intelligible and all 
bespeak the inherent motion of atoms and molecules when 
they are so circumstanced that the motion is free to exert 
itself. 

The phenomena exhibited by matter in all its phases, as 
systematized by these laws (and others of a highly technical 
character) have occasioned two great generalizations — the 
kinetic theory of molecular motion and the conservation of 



106 OUR WORLD 

energy. It is thus assumed that all matter is composed of 
separate molecules which are in constant motion ; that they 
are perfectly elastic, and in gases, wholly independent ; that 
in liquids and solids this free motion is limited by cohesion, 
and the speed of the motion is changed by temperature. The 
particles being perfectly elastic, their energy is never im- 
paired, and the different forms of the energy are mutually 
convertible one into another. It follows that, whenever an 
amount of energy is produced or absorbed in the formation 
of a compound, exactly the same amount is required to 
separate the constituents. To illustrate these principles by a 
familiar instance, a given quantity of coal by burning pro- 
duces the same amount of energy — which in turn may cause 
heat, light or electricity — as was taken, directly or indirectly, 
from the sun to produce the coal; and the components re- 
leased by combustion are then free to renew their activity by 
producing new combinations without loss of any part of 
their constitutional energy. 

It will now be seen by those who were not familiar with 
the kinetic theory of gases why the moon has no atmos- 
phere and that of Mars has become depleted. Free motion 
is always in a straight line ; variations are caused by other 
forces acting upon it. The molecules of a gas move in all 
directions ; but most of them collide with one another and 
rebound or are deflected. It is this motion of the innumer- 
able particles that causes the diffusion and the consequent 
pressure when stopped by the container. If the moon ever 
had an atmosphere it must have been speedily lost. The 
outer part of an atmosphere is not only the most rarified, 
but it is composed of the lightest free gases of the whole. As 
the external particles moving directly outward were no 
longer impeded and were moving with a velocity greater 
than the gravity of the moon could arrest, they plunged into 
space. This process continued until all the gases were lost. 
The same principle of course applies to all minor astronomic 
bodies. Mars, being larger than the moon, exerts a greater 
power of attraction, and its loss of atmosphere has been pro- 



WAYS AND MEANS 107 

portionally slower. The earth is massive enough to have 
held its atmosphere, which emanated from within, without 
substantial diminution. 

That matter never loses its potential energy is aptly shown 
by the materials contained in the meteors. These materials 
are held intact and inert in the absolute cold of space during 
the hundreds of millions of years since the formation of the 
solar system ; yet the instant they come in contact with the 
air their latent energies spring into action. After blazing their 
way to the surface of the earth any fragments that remain 
are as amenable to chemical action as any other material 
that might be converted in a crucible or a solution. 

Despite the steady progress of general chemistry during 
the first half of the nineteenth century, it gave little promise 
of becoming an exact science. Its laws were largely empir- 
ical and its science chiefly in classifying the already im- 
mense and constantly increasing multitude of separate facts. 
Several hitherto unknown elements had been discovered, 
and a great number of compounds, of which the composi- 
tion and properties were unknown or not fully recognized, 
were identified and analyzed; and the process is yet far 
from exhausted. The labor devoted to these researches and 
explorations of matter occupied the greater share of atten- 
tion. The field of organic chemistry enormously widened. 
Thousands of organic compounds had become definitely 
understood. For a long period there was supposed to be 
some vital distinction between organic and inorganic matter ; 
but the progress of investigation revealed no differences in 
the principles of their combination and the presence of none 
but familiar elements. When it was found that many of the 
organic compounds could be duplicated by synthetic methods 
— literally manufactured from the elementary ingredients 
wherever obtained — organic chemistry came to signify the 
system of compounds in which carbon is a factor. Some as- 
pects of this branch of chemistry will be more serviceably 
presented in their biological relations ; but the main fact is 
significant here as showing that all matter, however com- 



108 OUR WORLD 

bined, obeys the same laws of chemical change and is com- 
posed solely from the same body of primary elements. 
Naturally this gave a powerful impetus to operative chem- 
istry in all its phases and thus multiplied the concrete re- 
sults of chemical theory. Practical chemistry then began that 
expansion which has been quite unexampled in any other 
sphere of effort and has become an adjunct of virtually all 
the most important arts and industries. 15 

THE ELEMENTS 

It will be recalled that when the spectroscope was intro- 
duced the possibilities of astronomy were greatly enlarged 
and the science began a new development. A similar though 
lesser result followed in physical chemistry. The spectro- 
scope supplied a laboratory test that was even more in- 
fallible than in astronomy for detecting the presence of any 
element from the spectrum it gives when incandescent, the 
greater certainty being caused by the absence of intervening 
atmospheres or stellar gases and the proximity of the sub- 
stance yielding the light being analyzed. The theory of the 
spectral lines is the application of an ordinary mechanical 
principle. Light, being a series of waves of different lengths, 
according to the color of the rays, but all having the same 
velocity, is neutralized by passing through a gas containing 
the same elements that produce the light, the waves being 
stopped, absorbed, because the intercepting gas contains 
molecules having the same speed of vibration as those which 
yield the corresponding portion of the spectrum ; hence the 
blank or dark lines across it. On the other hand, bright- 
line spectra show the sources of the light to be such that 
they yield only part of the rays necessary to produce com- 
plete spectra, which can only result from white light. When 
a substance becomes gaseous and the gases are heated to in- 
candescence, their spectra are not continuous, but consist of 
separate bright lines. The number and position of these 
lines depend on the color of the total light emitted, this color 
being due to the particular variety of wave-lengths combined 



WAYS AND MEANS 109 

in the light. Since the atoms of each of the different ele- 
ments have a distinctive vibration, unlike that of any other 
element, the lines represent different wave-lengths, which 
have their individual places in the spectrum, where they are 
identified with absolute precision. From these facts it will 
be seen how important has been the function of the spec- 
troscope to chemistry and physics. 

It is now very generally assumed that there are 92 ele- 
ments, including certain of the group produced by successive 
transmutations from uranium and thorium. All have differ- 
ent atomic weights, ranging from 1.008 for hydrogen to 
238.5 for uranium. Only four between hydrogen and lead 
await discovery, while tw T o gaps in the radioactive group are 
yet unfilled. This progression early invited efforts to ad- 
just the elements then known to a system based on an 
orderly arrangement of the atomic weights. Several at- 
tempts were made to devise such a system, but the facts 
seemed too obstinate until Mendeleeff, an eminent Russian 
chemist, proposed the so-called Periodic Law. 

If the elements are arranged in the order of their in- 
creasing atomic weights, the properties vary from member 
to member of the series, but return to nearly the same value 
at certain fixed points in the series. It thus appears that, 
with certain exceptions, every eighth element so arranged 
has similar characteristics. All the members of each group 
tend to possess the same valence or combining power and 
their compounds to resemble one another chemically. More- 
over, this family resemblance is seen not only in their chem- 
ical but in their physical properties, such as specific heat, 
melting point and so on. Certain of the elements, it is true, 
do not appear to conform to the periodic law ; but its appli- 
cation is so striking in most instances that the exceptions 
may yet be explained and brought into harmony with the 
rule. Mendeleeff himself foretold that certain vacancies in 
the list of elements then known would be filled by the dis- 
covery of elements with the missing weights and with prop- 
erties which he specified. Some years later the rare elements 



110 OUR WORLD 

known as gallium, scandium and germanium were discov- 
ered possessing the weights and properties predicted by him. 
Besides these, the inert gases of the argon group — helium, 
neon, argon, krypton and xenon — were found partly as the 
result of search for the missing atomic weights, which they 
quite accurately fulfill. 

About 191 2, Moseley, a young English scientist, made the 
brilliant discovery that, arranged in the order of the in- 
creasing frequency of their characteristic X-ray spectra, all 
the known elements, so far as they have been examined, 
form a simple arithmetical series, each member of which is 
obtained from its predecessor by adding the same quantity. 
This fact would indicate that the inherent electrical energy 
of the atoms is the source whence all their properties are de- 
rived. Thus it is in physics, the science of energy, rather 
than in chemistry that the ultimate is to be sought. This 
brings us to the subject of electricity as the universal and 
dominant factor in the constitution of matter and the 
medium of the revelations which have been made in recent 
years. 

ELECTRICITY 

The progress of modern chemistry has been practically 
coincident with the development of electrical science, 
though in the early stages the fundamental connection was 
not fully perceived. In 1750, when Benjamin Franklin made 
his experiments and announced the dual nature of electricity, 
positive and negative, chemists were only beginning to grasp 
the significance of some of the more obvious properties and 
relations of matter and were quite without any clear con- 
ception of the factors underlying the phenomena of chemical 
reactions. It w r as not until 1799 that the production of an 
electric current by chemical means was discovered by Volta, 
who produced that result by alternate plates of copper and 
zinc separated by layers of cloth saturated with salt water 
or sulphuric acid. This was suggested by Galvani's famous 
experiment in 1790 (following what he noted through a 



WAYS AND MEANS 111 

casual incident), causing the spasmodic contraction of frog's 
legs by connecting the nerves and muscles with an arc of two 
metals. 

In 1800, by the use of the voltaic pile made with numer- 
ous silver and copper plates and cloths wet with salt solution, 
water was decomposed. This operation, now so simple and 
familiar, was one of the most important discoveries in 
science. It changed the whole trend of research which has 
led to the chemistry of the present day. The atomic theory 
itself was prompted by it. The experiment was soon tried 
with various materials and the process and the principle of 
electrolysis established with far-reaching results in both 
practice and investigation. 

Despite various theories advanced to account for it, the 
cause was not recognized until in 1833, when Faraday 
proved that the source of the energy was in the formation 
of zinc sulphate and the liberation of hydrogen through 
chemical change. The conversion of chemical energy into 
electrical energy is shown by the fact that the quantity of 
the substances decomposed is exactly proportional to the 
amount of electricity passed through the solution affected, 
(the electrolyte). Moreover, if the same current is passed 
through a series of electrolytes, the quantities of the various 
materials liberated are proportional to their chemical 
equivalents. 

It was long assumed that the change was due to the 
breaking assunder of the molecules of the substances de- 
composed; but, in 1885, Arrhenius, an eminent Swedish 
physicist, proposed a new hypothesis, which is now accepted 
as best explaining all the phenomena. By this hypothesis, 
the current passing through a dissolved or melted elec- 
trolyte simply directs the ions according to the electrical 
charges with which they are already invested and causes 
them to be discharged and thus restored to the common 
neutral state at the terminals of the current where they ap- 
pear. As this process will not be clear to those who have not 
followed developments in this field during recent years, it 



112 OUR WORLD 

is needful to define some of the terms to which the new dis- 
coveries and new theories have given rise. 

The Greek language, as usual, has supplied many of these 
terms. The word "electricity" itself is from the Greek for 
"amber", because of the well-known power of attraction 
possessed by that substance when rubbed. The word "elec- 
trolyte" is a compound of the words for "electric" and 
"solution", thus defining either the solution or the substance 
added to the solvent to produce what is termed a conductor 
of the second class. 

It should be stated in this connection that most substances 
— nearly all pure liquids, including pure water, the non- 
metallic elements and most dry compounds — are non-con- 
ductors of electricity. Substances that permit the passage of 
the current — for the most part, metals and their alloys — 
are known as conductors of the first class. All the electro- 
lytes are conductors of the second class. They allow the 
passage of the current, but at the same time are decom- 
posed by it or cause the decomposition of the terminals. The 
electrolytes are acids, bases, salts in solution or water highly 
heated. 

The term "electrolysis," the process of this decomposition, 
is aptly derived from the verb "to lose," combined of course 
with "electric." The terminals, at which the current enters 
and leaves the solution, are called electrodes, another de- 
scriptive compound of "electric" with the Greek noun for 
"path" or "road." The electrodes are either cathodes (down- 
ward paths) or anodes (upward paths). The positive ele- 
ments collect at the cathodes and the negative (non-metallic 
elements or radicals) at the anodes. Thus when the solute 
is decomposed into two kinds of materials they move toward 
the respective electrodes. In this condition they are termed 
"ions," from the Greek for "goer" or "traveler." 

The phenomena of the ions, as explained by Arrhenius, 
had long been studied in other conditions. By inserting the 
electrodes in a sealed glass tube filled with air at ordinary 
atmospheric pressure and increasing the force of the cur- 



WAYS AND MEANS 113 

rent to a certain degree, the air is unable to bear the strain 
and a spark is produced. If the air or other gas is expanded 
by removing a portion with a pump the character of the 
discharge changes. The manifestations of light and move- 
ment thus alter with the progressive rarity of the gas. Be- 
yond a certain degree of exhaustion of the gas the discharge 
refuses to pass, though the highest attainable vacuum still 
contains many millions of molecules per centimeter. When 
the current and the rarity of the gas are suitably adjusted 
the cathode gives rise to particles that move in straight lines 
and with great speed. As they strike the end of the tube the 
glass becomes phosphorescent. If a sheet of platinum, or of 
certain other substances, is suspended between the cathode 
and the other end of the tube a shadow is cast. If the par- 
ticles are focused upon an object its temperature is in- 
creased, and in many cases chemical changes are produced. 
They pass through thin sheets of metal, but are absorbed 
by thicker ones. 

These effects and others scarcely less remarkable naturally 
evoked profound interest and study; but the precise cause 
was not determined until 1897, when J. J. Thomson, by 
highly ingenious and intricate methods, demonstrated the 
entity of the electron. The name antedated positive knowl- 
edge of the thing itself. It was suggested in 1881 in recog- 
nition of the principle that alone seemed to account for the 
phenomena. 

The properties of the electron are independent of the 
nature of the gas and of the material of the cathode. Similar 
particles are emitted from the inert elements of the argon 
group, from many solids, metals red-hot or illuminated by 
ultra-violet rays, and radioactive materials. They no doubt 
are an important factor in many natural phenomena as yet 
obscure. It has even been surmised that the aurora is pro- 
duced by electrons discharged from the sun and moving 
under the earth's magnetic lines of force. 

The mass of the electron, as now determined, is %845 oi 
the hydrogen atom. "Imagine," said Lord Kelvin, "a globe 



114 OUR WORLD 

of water or gas as large as a football to be magnified up to 
the size of the earth, each constituent molecule being magni- 
fied in the same proportion. The magnified structurewould not 
be more coarse-grained than a heap of footballs." In gases, 
of course, the molecules are much further apart than in 
liquids ; and in liquids much more so than in solids. When 
it is stated that 40,000,000 molecules of air arranged close to- 
gether in a line would extend only one inch, the infinitesimal 
size of the electron becomes inconceivable by our ordinary 
senses ; yet by the perfection of scientific methods it is meas- 
ured with a degree of accuracy that admits of no question. 16 

The ion may be an atom or a molecule, such a hydroxl, a 
radical consisting of one atom of hydrogen and one of 
oxygen. When hydrogen ions and hydroxl get near one 
another they instantly fly together, forming a molecule of 
water. The positive and negative electrical forces are per- 
fectly balanced. When, therefore, molecules are neutral, as 
matter in a normal state always is, the positive force and the 
negative electrons with which they are invested are balanced. 
The effect of the current is to disturb this equilibrium which 
is soon restored when the current ceases. 

This action, and many others of similar kind, lend extreme 
probability to the view that most of the phenomena of nature 
are due, in the last analysis, to electrical attraction and re- 
pulsion. Perhaps the most singular circumstances in elec- 
trical manifestations is that, so far as known at the present 
time, so-called positive electricity never leaves the atom. 
The positive electron, if such there be, is unknown. The 
work appears to be performed wholly by the negative elec- 
tron, which is detached and added with perfect facility. 
Negative electricity, then, exists, only in the form of elec- 
trons. Normally an atom contains a certain quota of posi- 
tive electricity and a sufficient number of electrons to neu- 
tralize it. If by any means an electron is added or released, 
the balance is disturbed. 

The metals, as a rule, exert but a relatively weak attrac- 
tion on the electrons, hence they are better conductors than 



WAYS AND MEANS 115 

the non-metals, though variable in this respect. A current 
of electricity is caused by the passage of the electrons 
through the atoms or the spaces between them. The material 
movement of the electron is quite slow, only a small fraction 
of an inch per second; but the impulse is communicated 
from electron to electron with precisely the same velocity 
as light. Thus light, heat and electricity are kinetic kindred, 
and, in the ultimate, through the activity of the electron. 

It may be assumed that the radiant energy of the sun is 
due to the vast number of electrons it contains in a mobile 
state because of the intense temperature of that body. Since 
they exist in great numbers in the substance of a metal, it 
might be expected that, if the metal were highly heated, 
some of the electrons would pass off into the surrounding 
space; and this is readily proven to be a fact. Under such 
conditions, the emission of electrons is analogous to the 
evaporation of a liquid. 

The various phenomena of electrical motion, proceeding 
from the vibration and impulse of the electrons, are in their 
radiant characteristics like those of light and therefore ex- 
emplify the same laws of reflection, refraction, absorption 
and variable speed through different substances. And it is 
not unlikely that what is known as chemical affinity is the 
product of electrical action — positive elements combining 
freely with negative, this attribute being most energetic as 
the condition of the temperature becomes most favorable. 
Thus common salt is composed of the positive element of 
sodium and the negative element of chlorine. In view of 
such phenomena, it is not surprising that the hypothesis 
should have been ventured, far in advance of demonstration, 
that throughout the universe there are but two absolute 
elements, positive and negative electrical charges. 

THE X-RAYS 

The study of the electron, its entity and functions, was 
greatly promoted by the phenomena of the X-rays and 
radioactivity, made known shortly before the electron was 



116 OUR WORLD 

isolated and measured. The discovery of the X-rays, in 
1895, was received with more acute public interest than any 
other scientific announcement had been since the invention 
of the telephone. The fact that rays had been found which 
though invisible to the eye, penetrate certain substances and 
affect the photographic plate, seemed the crowning achieve- 
ment of a scientific century. But, despite the wonder of the 
discovery and the practical uses to which it was soon ap- 
plied, its true scientific import was the light it shed upon 
the fundamental sources of nature and the constitution of 
matter. 

The X-rays are produced whenever the cathode rays 
strike matter of any kind. They pass with little detriment 
through flesh, paper, wood and many other substances, in- 
cluding metals of small atomic weight, such as aluminum; 
but they are quickly absorbed by metals of high atomic 
weight, such as platinum, gold and lead. They are not ma- 
terial, like electrons, but are the result of motion produced 
in the target of the cathode rays and therefore possess the 
same characteristics as those of light ; but their wave-lengths 
are much shorter. For years no method was found to show 
that the X-rays proceed according to the familiar laws of 
light. No surface smooth enough had been used, and no 
material with sufficiently fine and regular grain to diffract 
and polarize them. In 1912, however, the difficulty was re- 
solved through the use of crystals. By this method a new 
and remarkable field of research was opened, and the atomic 
structure of matter was visibly demonstrated. 

Scientists had long regarded crystals as being very tangible 
evidence of atomic structure. That each of the very numer- 
ous substances which crystallize under suitable conditions 
should assume its own type of formation, was viewed as a 
plain indication that the different forms are due to definite 
and corresponding arrangements of the atoms composing 
them. And this was shown to be true by photographs taken 
by means of the X-rays. It thus appears that the atoms ar- 
range themselves in perfect planes and in a definite order in 



WAYS AND MEANS 117 

eacK kind of crystal. Because of the definite positions of the 
atoms, the crystal operates like a nearly perfect optical grat- 
ing of three dimensions. When, therefore, the X-rays are 
passed through it they reveal definite patterns caused by 
interference. By examining the position and intensity of 
the spectrum thrown by the crystal the distances between the 
successive planes of the atoms are computed. 

This method of investigation is still in its early stage 
and promises to yield even more fruitful results. Already 
it has been applied to some forms of liquid produced from 
certain organic substances heated slightly above the melt- 
ing-point. The crystalline arrangement found there can be 
altered by pressure ; but the molecules tend to restore them- 
selves to the ordered pattern where the process can freely 
exert itself. The laws that govern the manifold arrange- 
ments of the atoms in their ordered combinations, fixing 
their places and holding them in equilibrium apart from one 
another are as yet wholly unknown. After what has al- 
ready been learned as to the nature of matter, the impossible 
cannot yet be delimited. 

No less obscure is the system which underlies the vibra- 
tions of the atoms. The spectra of the various elements 
contain tens of thousands of lines, each one of which repre- 
sents a different period. In the case of carbon or iron alone 
the periods amount to thousands. Since each period is in- 
variable whenever and wherever produced, there must be 
a universal cause for each of these multifarious activities. 
As remarkable as the results of spectrum analysis have 
been, they fail to elucidate what are assumed to be compli- 
cated secondary vibrations within the atoms. Nor is the 
explanation of magnetic phenomena much further advanced. 
The principle announced by Mosely, before referred to, 
show r s that the atomic weights only approximate the periodic 
system and therefore that the true and exact periodic char- 
acter of the elements is based upon the X-ray spectra. 

The discovery of the electron and the X-rays gave to 
physical chemistry the prospect of becoming an exact science 



118 OUR WORLD 

and opened the way to a closer contact with the problem of 
the nature of matter than had even been conceived. 

RADIOACTIVITY 

Not long after the discovery of the X-rays, Becquerel, 
a French physicist, conceived the idea that there might be 
some relation between the fluorescence produced by the 
cathode rays and the natural phosphorescence of certain 
well-known substances, though he found that they were 
not the same. But his investigations resulted in the dis- 
covery of the radioactivity of uranium, which has a radia- 
tion in some respects similar to the X-rays and in others 
quite different. He then suggested to M. and Mme. Curie 
the possibilities of investigating the uranium ores. They 
took up the work with zeal and skill and soon found some 
of these ores were more active than uranium itself. Obvi- 
ously, therefore, there was some substance more intensely 
radioactive than uranium. The particular substance selected 
for analysis was pitchblende, a highly complex mineral con- 
taining many elements, found in but few and widely sepa- 
rated regions. After one of the most complicated separa- 
tions known to chemistry several new radioactive elements 
were found, notably radium, which has proven of greater 
public interest than the X-rays and of more importance to 
science. While it was easy to trace during the entire pro- 
cess, as its presence could always be detected by the electro- 
scope, the difficulty in isolating it may be inferred from the 
fact that a ton of pitchblende yielded only a few milli- 
grams of radium bromide. 

Notwithstanding radium is a result of successive disinte- 
grations of uranium and a series of its products and is itself 
in a state of constant disintegration, it is regarded as an 
element. It has a perfectly definite spectrum and an atomic 
weight of 226. It is the most concentrated form of energy 
within the range of human knowledge, and is a million and 
a half times as radioactive as the uranium whence it is de- 
rived. The source of this energy is inscrutable and inde- 



WAYS AND MEANS 119 

pendent. The rate of its discharge cannot be hastened or 
retarded by any known means. Radium is self-luminous. 
Its radiations produce chemical reactions and decompose 
the most stable chemical compounds. They ionize the media 
through which they pass, even such dielectrics, or non-con- 
ductors, as pure liquids and such solids as paraffin. They 
liberate heat, and this indifferently as well at the lowest 
as at ordinary temperature. 

All radioactivity is embraced within three distinct types, 
known as alpha, beta and gamma rays, named after letters 
of the Greek alphabet. Radium gives off all three. The 
determination of the nature of these rays was simplified by 
the precise knowledge already obtained concerning the elec- 
tron and the X-rays. The alpha and beta rays are mate- 
rial, being particles. The gamma rays are not material, but 
are electrical impulses that attend the discharge of the beta 
rays. The alpha particle is the swiftest of any known, hav- 
ing a velocity about one-tenth that of light, thus manifest- 
ing an enormous kinetic energy. It affects the photographic 
plate and excites fluorescence. Its mass is about four times 
that of the hydrogen atom, and because of its size it does 
not penetrate matter. It carries two units of positive charge. 
It is the helium atom! The beta rays are electrons, and 
the gamma rays, which always attend the beta rays like 
waves of sound from the shot of a gun, are identical with 
the X-rays, being electrical radiations that result when elec- 
trons are violently expelled from the atoms. The gamma 
or X-rays are usually of two distinct wave-lengths. The 
secondary ones are caused by the impact of the beta rays 
upon the anti-cathode. Most elements give out both these 
characteristic wave-lengths, which form the X-ray spectrum. 

The distinctively radioactive substances appear to be de- 
rived from uranium and thorium, the two heaviest and 
therefore most complex elements. All are unstable, else 
they would not be radioactive, but most of them are so 
unstable that they endure in distinctive forms for only brief 
periods. Thirty-five of these radioactive substances have 



120 OUR WORLD 

been discovered and their positions in the three main series 
determined. While each of these substances is regarded as 
a distinct chemical element, it differs from ordinary elements 
in the spontaneous emission of special radiations through 
which it is disintegrated, each in its own way, with a degree 
of energy vastly greater than is shown in any form of chem- 
ical reaction; and this cannot be affected or controlled by 
any known means. 

THE CONSTITUTION OF MATTER 

Science is far from arrival at final conclusions as to the 
significance of the phenomena here outlined and many others 
of a highly technical character to which investigators are 
directing a degree of attention far surpassing in minute pre- 
cision any methods previously known. The structure of 
the atom now regarded as most probable is based on the 
"nucleus theory" of Rutherford. "A heavy atom," he says, 
"is undoubtedly a complex electrical system consisting of 
positively and negatively charged particles in rapid motion. 
The general evidence indicates that each atom contains at 
its center a massive charged nucleus or core of very small 
dimensions surrounded by a cluster of electrons probably 
in rapid motion which extend for distances from the center 
very great compared with the dimensions of the nucleus. 
Such a view affords a reasonable and simple explanation 
of many important facts obtained in recent years, but so 
far only a beginning has been made in the attack on the 
detailed structure of the atoms — that fundamental problem 
which lies at the basis of physics and chemistry." 

The position and the character of the motion of the elec- 
trons within the atom is now the chief subject of investiga- 
tion, with the prospect of final demonstration that will ac- 
count for all the phenomena as yet obscure. 

Potassium and rubidium are slightly radioactive, and it 
may be that as methods and measurements are perfected 
this property will be found characteristic of other elements. 
If all the elements are subject to disintegration through 



WAYS AND MEANS 121 

this or other causes, they must have been formed by evo- 
lution. This conception arose long before the discovery 
of radioactivity as a logical inference from the revelations 
of the spectroscope. The form of distinct matter appears 
to begin with the elementary gas nebulium, the presence of 
which in certain nebulae is shown by its spectral lines. He- 
lium was likewise known in the same way long before it 
was found to exist on the earth. The other and more com- 
plex elements, as shown by their increasing atomic weights, 
appear in the spectra of the older stars, thus affording some 
evidence that the elements are evolutionary products of 
primordial forces, whatever they may be. For these reasons 
it will be seen why scientists tend more and more to the 
opinion that electrical forces are the things and matter in 
all its forms but the manifestations. 

This outline of the more prominent features of chemical 
science at least shows the marvelous progress that has been 
made toward positive knowledge of the ultimate fundamen- 
tals. In the light of the present state of that knowledge 
and the promise of future additions to it, the barrier of 
the unknowable has again receded. At a very recent period 
the atomic theory was questioned in high quarters ; but the 
verity of the atom is now undoubted, though it is no longer 
the indivisible and indestructible thing that seemed essential 
to its existence. It is manifestly a product and the seat of 
the energies that actuate the universe. In the mechanism 
of that minute but mighty engine may yet be found the 
clue to those mysteries that lie behind the most familiar 
phenomena. What is chemical affinity ? Why do the same 
elements combine in different ways to produce diverse sub- 
stances ? Why do various radioactive elements have differ- 
ent atomic weights, while they cannot be distinguished other- 
wise ? Why do certain elements of the same atomic weights 
show radical chemical differences ? All these questions may 
yet find answer in the electrical structure of the atom. The 
secret of gravitation, the most baffling of all, may likewise 
be hidden in the nucleus of the atom. 



122 OUR WORLD 

The positive appears never to be associated with a mass 
smaller than the hydrogen atom, which, therefore, in a 
neutral state holds but a single negative electron; yet this 
atom is nearly 2,000 times as heavy as the electron, which 
is a million million times as dense as the atom and is prob- 
ably spherical in form. From these facts it will be seen 
what an endless scope there is for different combina- 
tions of the positive and negative forces in the atomic nuclei 
through the long series of the distinctive elements pro- 
gressively increasing in their weights, and how readily 
conceivable it is that all manifestations of matter whatsoever 
are due to differences in the quantity and disposition of the 
electrical energies. 17 

Equally interesting and even more obscure is the problem 
of the transmission of light. There is no reason to doubt 
that light waves are electrical in character. There seems 
to be no fundamental difference between waves of light 
and the wireless waves of telegraphy, except that the latter 
are much longer and of slower vibration. The progress 
of knowledge as to the nature of matter has inevitably led 
to reconsideration and revision of the former theories con- 
cerning the physics of the ether. The subject is under 
profound scrutiny and gives good promise of a better under- 
standing of the medium by which the forces of the universe 
are exerted. "To be living in a period/' says Millikan, 
"which faces such a complete reconstruction of our notions 
as to the way in which ether waves are absorbed and 
emitted by matter is an inspiring prospect. The atomic 
and electronic worlds have revealed themselves with beau- 
tiful definiteness and wonderful consistency to the eye of 
the modern physicist, but their relation to the world of 
ether waves is still to him a profound mystery for which 
the coming generation has the incomparable opportunity of 
finding the solution." 



CHAPTER V 
LIFE 

THE BEGINNING 

FOR eons the earth was devoid of life and must again 
become so, from precisely opposite causes. The organic 
cycle is now in an advanced phase, and its future duration 
as indefinite as its beginning. The process of its origin 
is the most obscure problem of science. 

The paramount fact in the history of life is its evolution. 
Despite the conflict of opinion in the past, the evidence is 
now decisive. Whenever in any branch of science a striking 
fact, however incomplete, has been discovered, it has led 
to more ample knowledge. The odds and ends of natural 
evidence, fragments of universal truth, discerned at different 
times and in many places, either fit to perfection or deter- 
mine the outlines of complete ideas. The progress of science 
has been largely the coordination of these fragments and 
the bold pursuit of the logic it has prompted. In no prov- 
ince of investigation has this method been more fruitful 
and conclusive than in paleontology and its related fields. 

Thus far no evidence has been found to show that chem- 
ical combinations in any circumstances spontaneously pro- 
duce life. If, however, life began as the normal action 
of inherent properties of matter under impelling conditions 
of environment, which science is obliged to assume, the 
original forms must have been of the simplest types, so 
minute and delicate that physical proof of their existence 
could not be preserved. For many millions of years after 
nascent life became possible and more complex organisms 
developed even to a degree that might have become fossil- 
ized, the accumulated strata of later geologic ages, piled to 
a thickness of thousands of feet above them, would have 

123 



124 OUR WORLD 

obliterated all traces except those of a chemical character. 
Most of the rocks of pre-Cambrian time now known are 
thus metamorphic, compressed by enormous weight and crys- 
tallized by heat. 

Yet chemical proofs of life are abundant in the rocks 
of those remote ages. Immense deposits of graphite, mani- 
festly the carbonaceous residue of minute plants of marine 
origin, are found in both the Archeozoic and the Protero- 
zoic eras. These proofs, though indirect, are positive. The 
only natural means by which carbon is separated from the 
oxygen, with which it forms carbon dioxide, is through 
the agency of protoplasm and sunlight. The leaf-green 
(chlorophyl) of plants enables the tissues to decompose the 
carbon dioxide, absorbing the carbon and giving off the oxy- 
gen. When, however, dead organic material is removed, 
as in sediments, from contact with the air and its bacterial 
swarms, decomposition is arrested and the elemental carbon 
is retained in the deposits instead of reuniting with oxygen 
in the ordinary course. Such was the origin of graphite; 
at all events, this is the only known explanation of its 
presence in these ancient geologic formations, and it is in 
full accord with the probable conditions. 

The opinion has long been held by some geologists that 
certain forms of limestone as well as hematite and magnetite 
iron-ores in the Archeozoic rocks furnish additional evidence 
of life at that period. It is possible that the limestone might 
have been formed without organic aid; but denitrifying 
bacteria, by taking advantage of the calcareous salts in the 
waters, may have been the cause. The case is somewhat 
stronger for organic agency in the formation of the iron- 
ores. They existed originally as ferrous carbonate and fer- 
rous silicate. Their subsequent change to the ferric form 
implies the presence of free oxygen and this in turn suggests 
organic causes. These conclusions are not as yet entirely 
demonstrated, but the facts point quite clearly to sources of 
future knowledge that will abundantly fill the present gaps 
in the early course and character of organic evolution. 



LIFE 125 

There are irresistible reasons for assuming a vast period 
of bacterial life prior to plant and animal forms however 
minute and primary. Bacteria are a necessary factor in the 
organic processes of nature, and must have been so from 
the beginning. Without bacteria both land and sea would 
soon be uninhabitable ; hence it may be assumed that during 
a very long period of time both were prepared by bacterial 
agencies for the evolution of plant and animal organisms. 
Certain forms of bacteria derive their energy and nutrition 
directly from inorganic compounds and could have thrived 
as soon as air, earth and water started chemical reactions. 
Whatever may have been the pioneers of life, bacteria ap- 
parently occupy a position midway between them and the 
definite cell structure of the algae, the earliest and simplest 
forms of plant life known to have existed. 

THE FIRST PLANTS 

It is not unlikely that early forms of algae, as of bacteria, 
still survive through the lapse of more than 50,000,000 years. 
Such phenomena are characteristic of some other types both 
of plants and animals, though the vast majority have be- 
come extinct after the rise of others, which bear the un- 
mistakable evidence of their lineage. Nor is the survival 
of primitive forms less notable than the fact so often demon- 
strated through geologic history that a species once extinct 
has never reappeared. Yet these facts are strong proofs 
of the principle of evolution. The precise conditions that 
attended the rise of previous types cannot in the nature of 
things recur. Changed environment necessarily produced 
different results, exterminating old forms without succes- 
sion or evolving new ones through adaptation. Obviously 
the simplest organisms would be the least affected and would 
be most widely distributed; hence the new forms would 
originate in circumstances more or less limited or local, while 
elsewhere the old, without the compulsion of necessity or 
the stimulus of more favorable conditions, would continue 
unchanged. The algae are of peculiar interest not only be- 



126 OUR WORLD 

cause of theif primitive character and persistence, but of 
also illustrating the fundamental process of evolution which 
has prevailed through both kingdoms of life on the earth 
from the period of their origin. 

The algae were the source of the enormously diversified 
order of Cryptogams — plants that produce no flowers or 
seeds. The algae and allied growths are technically known 
as Thallophytes, as they have no roots, stems or leaves. 
They range from single nucleated bits of protoplasm to the 
gigantic Macrocytis of the South Seas, including the desmids 
and diatoms, which have existed in inconceivable myriads 
during many geologic periods, and the sea-weeds that flour- 
ish in tropical waters. The minute forms abound in stag- 
nant pools and damp soils and spread over wet stones and 
the bark of trees. Being the simplest of all plants, each 
variety is composed of only one class of cells, which draw 
nourishment directly from inorganic substances held in solu- 
tion by the waters or surrounding moisture. The primitive 
forms have but a single cell. Higher forms have branched 
or unbranched chains, filaments or sheets of cells, while the 
still more complex types bear a close resemblance, in ap- 
pearance rather than in fact, to familiar plant growths. The 
single-celled varieties increase by division. In some Crypto- 
gams the process of reproduction is quite complex, being 
accomplished by the union of germ and sperm cells, neither 
of which is capable alone of further development, thus 
illustrating the undoubted origin of the great order of 
Phanerogams, the flowering and seed-bearing vegetation 
that appeared much later. 

The fungi, with their thousands of distinct varieties, are 
closely related to the algae, being parasite forms, devoid of 
chlorophyl and thus unable to subsist on inorganic matter. 
The lichens, also of many kinds, are of the same origin. 
They are symbiotic or consorting organisms, composed of 
the higher fungi in union with single-celled and threadlike 
algae, one supplying the water and the other the carbon. 
This symbiosis (from the Greek for "life together") is 



LIFE 127 

characteristic of certain of the bacteria, which it is reason- 
able to suppose were ancestral to the primary algae. 

The most significant feature of these different phases of 
primitive plant growths, and which continues through all 
subsequent developments, is that in whatever direction the 
course of evolution has taken there has been an unbroken 
line, one form insensibly grading into another through some 
slight modification or addition of function, which is always 
and necessarily attended by a corresponding change in phys- 
ical form and character. The outstanding principle in nat- 
ural history is that conditions give rise to function, and 
function simultaneously requires an appropriate organiza- 
tion for its exercise. This is the key to the evolution of 
life and the most mysterious attribute of nature. 

THE FIRST ANIMAL ORGANISMS 

The tangible evidence of the earlier forms and stages of 
animal life is less definite and complete than that of the 
primary plants. It is unknown when the Protozoa, single- 
celled types of animal life, first appeared; but it must have 
been after a long bacterial stage and possibly not until the 
algae had arisen. Animal life, being chemically dependent 
upon bacterial and plant life, could not have existed without 
them. The medium of animal origin was water, probably 
at the start the water of moist soils containing the neces- 
sary elements brought there by erosion and combined by 
natural means into forms suitable for animal assimilation. 
The simplest Protozoa subsist on bacteria, and the more 
advanced on the minute algae. Thus in the primordial con- 
ditions, after geologic and bacterial action had supplied the 
waters with the necessary materials and brought forth luxu- 
riant plant life, though of small and simple kinds, the Pro- 
tozoa were provided with the means of subsistence and the 
environment for increase and evolution. 

The same general considerations as to the persistence of 
the earliest plant organisms and the lack of fossil proofs 
of their existence in the pre-Cambrian formations apply to 



128 OUR WORLD 

the primitive animal types. Before the appearance of the 
Metazoa (many-celled), that began to use lime and other 
minerals in their structures, the insubstantial remains of 
the previous simpler forms could scarcely resist destruction 
in the metamorphic rocks where the evidences might other- 
wise be found. Nevertheless, there are two reasons that 
point to an evolution essentially parallel with that of plant 
life. From the period where fossils show the stages of 
animal evolution and geologic strata record the time, that 
process is clearly demonstrated; hence the conclusive pre- 
sumption that the prior course was governed by the same 
principle. Equally decisive is the complete existing chain 
backward to the infusoria, the amoebae and the monera, the 
latter being little more than specks of protoplasm with no 
other function than to assimilate food by surrounding it 
and multiplying by cell division. Thus the early history of 
animal life is in all respects analogous to that of plant life, 
showing a similar gradual increase of function and complex- 
ity of organization. The changes radiated in many direc- 
tions and resulted in thousands of forms that finally lost 
all resemblance to one another and require the eye of an 
expert to trace their relationship. 

THE INVERTEBRATE ORDERS 

The earliest geological evidence of animal life has thus 
far been found only in the late Proterozoic. It is not only 
scanty but indicates types much later than the original Pro- 
tozoa. The Radiolaria, advanced forms of that order, 
minute but inclosed in durable tests of solica, were then 
in existence; also the Annelida, composed of ringed seg- 
ments like the common earthworm, left their trails and 
burrows in the sediments of that time. These are proofs 
that the invertebrate classes were already well established 
and the sources organized for that diversity of form and 
function which renders the Paleozoic era the most graphic 
in the whole panorama of natural history. 

The most notable feature of the Cambrian strata is the 



LIFE 129 

abrupt appearance of fossils in abundance and variety and 
in advanced stages of evolution. There is manifestly an 
immense loss of the previous record, to a great extent, pre- 
sumably, by erosion during a long period of the late Prote- 
rozoic. From all countries at least a thousand Cambrian 
species are known, about half of them North American. Of 
these the most important and the most numerous were the 
trilobites. They became extinct before the close of the Paleo- 
zoic ; but during their long career some two thousand kinds 
appeared. They were doubtless exterminated because their 
armature, though of a horny substance, which has preserved 
the fossils, could no longer protect them after the alert and 
voracious fishes appeared, about the time when the trilobites 
attained their greatest development in size and numbers. 

It is assumed from their structure that they evolved from 
wormlike ancestors. Their bodies were made up of seg- 
ments articulated in three divisions. They usually had 
compound eyes and breathed, so to speak, through their 
biramous limbs by means of long hair-like appendages in 
which the circulating blood drew oxygen from the waters 
in which they lived. They were able to swim freely and 
to crawl and burrow along the bottom, the scavengers of 
their time. They multiplied sexually and during growth 
repeatedly cast off their shells. The peculiar interest attach- 
ing to them is due to the fact that they and their progeni- 
tors are the sources of the entire phylum of the Arthropoda 
(joint-footed), with articulated or segmented bodies and 
limbs. It includes so diversified an array as the scorpions, 
crustaceans, centipedes, insects and mites, which later on 
branched into the multifarious life of the planet. 

Another of the great phyla already well established at the 
beginning of the Cambrian was that of the Mollusca. The 
forms then extinct were ancestral to the many species that 
appeared through subsequent ages. The most complex order, 
the Cephalopoda (head-footed), embracing such varieties as 
the nautilus, octopus, cuttlefish and squid, began the record 
of their evolution during this period. Likewise the Gas- 



130 OUR WORLD 

tropoda (stomach-footed), such as limpets, drills, periwin- 
kles, whelks, conchs and snails, and the Pelecypoda (hatchet- 
footed), comprising oysters, clams, muscles, cockels, scal- 
lops and all their numerous relatives, were present in small 
and primitive forms, so that their history is graphically 
written with their shells through subsequent geologic strata. 

Of even greater importance to geology than any of these 
higher types of the invertebrates are the Brachiopoda (arm- 
footed), a lower class of shelled animals than the molluscs, 
which they externally resemble, though of different origin 
and internal structure. The term applied to these mol- 
luscoids is a misnomer. It was early adopted through mis- 
apprehension as to the use of the brachia or arms, not 
for movement, but to obtain food and oxygen. The shells 
of this phylum are strewn in such profusion and variety 
through the Paleozoic and later that they have served, like 
the trilobites, as an invaluable index for the correlation of 
the strata. At the beginning of the Cambrian they existed 
in great numbers but few forms, the variety gradually in- 
creasing and the shapes slightly changing with time and 
conditions. The original species were mostly Particulates, 
the shells enclosing them not being hinged ; and they became 
the more general type at later periods. Over two thousand 
kinds have been found in North America belonging to the 
Paleozoic; and over one hundred and fifty characteristic 
forms exist at the present day, the shells of many of them 
being familiar objects in the sands of the seashore. 

It will here suffice merely to allude to other and lesser 
phyla — the Echinodermata (spiny-skinned), such as star- 
fishes, sea-urchins, sea-cucumbers and sea-lilies; and the 
Coelenterata (hollow intestined), such as hydroids, jelly- 
fishes and the coral-polyps. They, like a great variety of 
wormlike types and sponges, are represented in the Cam- 
brian by primitive forms. They afterwards differentiated 
into more complex classes, which ultimately became extinct 
or graduated into persistent forms more or less changed in 
detail, but retaining their distinctive features. 



LIFE 131 

The chief significance of these facts lies in the circum- 
stance that all of the great phyla or general types of animal 
life below the vertebrates had attained their permanent divi- 
sions and characteristics at the time when paleontology sup- 
plies the first evidence. This advanced degree of evolution 
justifies the conclusion that geology gives only the later 
chapters of natural history, and that the time required for 
organic life to reach the diversified and established phases 
revealed by the Cambrian must have been quite as long as 
that which has since elapsed. 

When we consider how small a proportion of the life 
extant at any time leaves fossils even under the most favor- 
able conditions, we may readily conceive how numerous 
were the creatures that teemed in the waters of the Cam- 
brian. Animal life was yet limited to the water ; and judging 
by those types, it is not possible that land species could then 
have existed. Discoveries in recent years, particularly in 
regions of western North America, which were submerged 
before and during the early Paleozoic, aid the expectation 
that knowledge of life in the pre-Cambrian will be greatly 
enlarged; and no scientist doubts that the results will be 
in perfect harmony with the principles of evolution manifest 
during all subsequent time. 

The duration of the Cambrian is usually estimated at 
some 3,000,000 years and of the combined Ordovician and 
Silurian, 6,000,000 years. The physical limits of these 
periods are defined clearly enough; but naturally the rise 
and fall of species do not accord with geological divisions. 
The processes of evolution are by infinitesimal changes in 
structure through the unknown factor of life that enables 
the organism and its successors to adapt themselves to the 
environment. The changes have therefore been so slow 
and gradual that enormous lapses of time have intervened 
between the distinct phases of development which have cre- 
ated the diversity of species now arranged in the classified 
order of their fossils in the great museums of the world. 

So far as now known there is not a living thing upon the 



132 OUR WORLD 

earth at the present time but has a geneology running back 
to the dawn of life in the Archeozoic; yet the pedigree is 
not decipherable when the lines of descent merge into the 
primitive sources. Nevertheless, the underlying principles 
which have governed the phenomena of life are clearly 
shown by the more salient facts that stand out in strong 
relief like great events in human history. 

The Ordovician and Silurian, unlike the ensuing period, 
were characterized by gradual transition rather than revo- 
lution in biological development. The invertebrate types 
were approaching that stage when evolution seems powerless 
to proceed further in certain directions except to increase 
the size or change the detail of the most advanced species. 
Some orders multiplied in variety and numbers and reached 
the acme of their activity, as shown by the vast and diversi- 
fied coral and limestone formations of that time. Others, 
having attained their climax, were waning toward extinction. 
Some idea of the general character of the mid-Paleozoic 
may be gained from the fact that the Ordovician has yielded 
five times as many forms as the Cambrian; and a similar 
ratio of growing diversity marks the Silurian as compared 
with the Ordovician. 

THE FIRST VERTEBRATES 

Out of this increasing welter of biologic detail two great 
and prophetic facts arrest attention. It has always been at 
such stages that new departures have been made. It was 
evidently then that the ancestors of the invertebrate terres- 
trial hosts emerged from the waters and started that rami- 
fication of orders and species which were eventually to invade 
the land with swarming myriads in an infinitude of forms. 
Moreover, it was then that the vertebrates made their ap- 
pearance, small in size, simple in structure and few in num- 
bers. The two facts that justify this conclusion are the 
presence of scorpions, the first known air-breathing crea- 
tures, and the fossils of the first known fishes. 

At the close of the Devonian the life of the world had 



LIFE 133 

assumed a new aspect. On the land as well as in the waters, 
plant and animal life, from lowly beginnings and through 
tortuous progress, had at length amassed from the sun and 
elements such a store of vital energies for reproduction and 
sustenance that organic development was greatly acceler- 
ated. The Devonian earth had not only inherited the accu- 
mulated results, but multiplied their potentialities. Thus 
time and circumstance had invested this period with charac- 
teristics that render it, if not the most important, at least 
the most decisive in organic history. In a general sense, 
the future of species was then determined. The back-bone 
and the lungs were established, and the trend of evolution 
fixed in necessary accord with the general planetary con- 
ditions. 

Whatever may have been the original vertebrates, the 
fishes were the first to develop the spinal structure with 
permanent success. The actual course of their evolution is 
still undiscovered ; but the probable stages are quite clearly 
deduced from existing types of fishlike creatures with in- 
cipient vertebrae. It is assumed from the nature of the first 
fossils and the localities where they were found that the 
fishes originated in inland waters and afterward spread to 
the seas, rapidly becoming the dominant life. The chief 
reason for the absence of fossil proofs of the antecedents 
of the known fishes is that the original forms were very 
small and without hard parts. None of the many species 
from the Devonian had a bony vertebral structure. Even 
the sharks, then as now, were without bones except their 
teeth and the spines in their fins, which thus furnish evidence 
of their ancient origin. They are the most primitive of all 
true fishes at the present time, not only because of this, but 
of their archaic organs, notably the gill-slits in the throat. 

As there were several distinct classes early in the career 
of the fishes it is possible that they originated independently. 
The oldest of these — the Ostracoderms (bony-skinned), 
heavily armored and sluggish, without a skeleton, but with 
a gristly spinal column of a simple kind — wholly djs- 



134 OUR WORLD 

appeared before the close of the Devonian. Yet they must 
represent a relatively late stage in the scale of vertebral 
evolution from probable pro-fish forms in the Cambrian 
or earlier of which no fossil traces remain. 

Among all the groups common in the Devonian, but now 
extinct or represented by modified descendants, the most 
important in scientific interest are the Dipnoi (double- 
breathing) or lung fishes. Species of these still survive 
in the rivers and marshes of Australia, Africa and South 
America. The original stock that produced them and the 
fringe-finned ganoids are regarded as the source from 
which the amphibians and through them the reptiles and 
mammals have been derived. But here, as in so many 
other instances of the rise of new orders, the precise link 
is missing between the first known air-breathing fishes and 
the stock below from which they branched in one direction 
and the amphibious salamanders in another. This is ex- 
pectantly sought in the Devonian and may yet be found 
even in the Silurian. The distinction of the lung-fishes 
is the double office of the air-bladder, which serves in times 
of drought as an organ of respiration in place of the gills. 
It returns the aerated blood directly to the heart and is 
therefore analogous to the lungs of the higher vertebrates, 
unlike the systems of most other fishes, in which the blood 
is carried from the bladder through the circulation before 
reaching the heart. It is a forward out-growth of the 
digestive tract and doubtless arose from the conditions of 
feeding and breathing in shallow waters where the original 
stock evidently appeared. 

THE FIRST VEGETATION 

The fossil indications of land plants during the Devonian 
are scanty but suggestive. It is certain from the great luxu- 
riance of the Carboniferous, or Pennsylvanian, that in the 
Devonian and perhaps in the late Silurian many lands were 
decked with verdure, and forests truly primeval flourished 



LIFE 135 

in many regions. The giant forms and enormous masses 
of vegetation that entered into the Coal Measures point to 
a long interval of probation and development before the 
original minute and delicate land flora, as the earliest must 
have been, could have reached such an advanced stage; for 
it was not until the upper Devonian that any plants acquired 
the woody tissue necessary to preserve them as coal or 
fossils. As the coal floras, which are the sources of most 
of the present knowledge of the primitive land plants, in- 
clude some three thousand species, botanical science is con- 
fronted at the very threshold with a degree of complexity 
and diversity that still present intricate problems of origin 
and heredity. However, a mere outline of the more impor- 
tant plant forms of that period will give some idea of the 
forests that choked the swamps where the future coal mines 
of the world were laid. 

The majority of the plants then existing were propagated 
by spores, which in the larger varieties were shed from 
cones in great numbers and scattered widely by the winds. 
They united and took root in profusion in the rich, moist 
soil; and their rapid growth was continuous owing to the 
genial climate that prevailed over most of the earth and 
throughout the year. The seed-bearing plants were in their 
youthful stages, while the flowering types were yet in their 
infancy. The largest and most abundant growths were the 
Lycopods (wolf's foot, from the form of the roots), of 
which there were more than two hundred species, the most 
common being the "scale trees" and the "seal trees." They 
often reached a height of over a hundred feet, with cor- 
responding girth. The wood was soft and spongy, inclosing 
a pithy interior. The scale trees, which in type were giant 
club-mosses, forked at a considerable distance from the 
roots and bore long, thickly set, needle-shaped leaves that 
dropped from the trunk and the older branches. The leaf 
bases thus exposed were arranged symmetrically and re- 
sembled scales. The seal trees were not usually as tall 
as the scale trees, but stockier with few or no branches 



136 OUR WORLD 

and with stiff, grasslike leaves of greater size. The older 
leaves were shed in the same way as those of the scale 
trees, but the leaf bases were of other shapes and arrange- 
ment, thus presenting a different appearance. The seal 
trees died out toward the close of the Carboniferous, leav- 
ing no descendants ; but the scale trees are still represented 
by such diminutive forms as the trailing club-mosses and 
the ground pines. 

Another varied group known as the Horsetails were com- 
mon at that period. The larger ones attained a height of 
ninety feet, the slender stems or trunks being of a pointed 
and rushlike form, hollow or filled with pith, and putting 
out leaves of different shapes arranged in whorls around 
the joints. The ferns were abundant and many of species, 
ranging from small plants to huge tree-ferns, resembling 
those now found in the tropics. The modern types, how- 
ever, were a later evolution from the early stocks. There 
were also numerous species of seed-ferns, which soon be- 
came extinct, being transitional to higher groups. Equally 
important in the flora of the Carboniferous were the Cor- 
daites, named after Cor da, an eminent paleobotanist. They 
were the dominant Gymnosperms (naked seed) of the Paleo- 
zoic and numbered many species. They reached great 
heights, some having huge, strap-shaped leaves that grew 
from branches well toward the tops, and bore small male 
and female flowers that developed seed clothed with husks. 
This group appears to have been a composite of several 
features of the great orders of that time in which modern 
botany finds the origin of the vegetation so enormously 
diversified and adapted to the varied geographic and cli- 
matic conditions. But none of the Angiosperms (covered 
seed), the great phylum which now embraces most of the 
vegetation of the world — grasses, cereals, bamboos, palms, 
orchids, forest trees and flowering plants generally — had yet 
appeared. 

This remarkable development of plant life was accom- 
panied by similar phenomena of animal life. The closing 



LIFE 137 

periods of the Paleozoic Age were equally significant in 
both phases of organic evolution ; and the coal deposits have 
furnished the principal records of both, which, for like 
reasons, are much less complete in the earlier stages than 
after the conditions of the Carboniferous became so per- 
fectly suited to the preservation of fossil history. 

INSECTS 

The thousand or more species of insects from the Penn- 
sylvanian and Permian are all supposed to have arisen from 
a primitive type derived from the trilobites. All the known 
early forms passed their larval stage in the water. While 
there are few indications of insects until the Pennsylvanian, 
there can be little doubt that the great development and 
different forms which then existed must have been preceded 
by a long period of evolution. The direct line of the pri- 
mary type, the first dragon-flies, attained great size. Speci- 
mens have been found measuring twenty-nine inches across 
the wings. Among the existing old families the cockroaches 
hold a distinguished position. More than five hundred kinds 
have been found in the Carboniferous of various lands, 
some of them three or four inches in length. The grass- 
hoppers have a lineage almost as ancient, and the spiders 
even longer, but they had not yet begun to spin. 

As numerous as the insect species were then, they were 
few as compared with the many hundreds of thousands 
which have since flourished in the many unlike regions of 
the world. The chief cause of this later multiplicity was 
the great diversity of environment that began in the Per- 
mian because of the increasing cold and aridity and the 
inception of climatic zones and seasonal changes. From 
these conditions arose many new orders that lost their 
amphibious character, developing the modes of reproduction 
and metamorphosis that now prevail, with intervening dor- 
mant periods brought about by cold weather and the lack 
of food. 



138 OUR WORLD 

THE AMPHIBIANS 

Nor was this variable factor of heat and cold less de- 
cisive in its effects upon other classes of animal life. The 
amphibians, which in the highly favorable circumstances of 
the time, reached the climax of their evolution in the lower 
Permian, were markedly affected by these changes. Their 
stocks were able to adapt themselves to the new conditions 
and continued to advance through the reptiles toward the 
mammalians, while the more highly organized were power- 
less to change and were therefore doomed to extinction — 
a phase and a proof of evolution often witnessed through- 
out the history of plant and animal life. 

The only evidence now known of amphibians in the Devo- 
nian is a single foot-print indicating a creature somewhat 
like a salamander about three feet in length. From the 
lower Carboniferous, or Mississippian, the proofs are 
sparse; but that the amphibians were present in ever in- 
creasing number and variety is apparent from their rapid 
progress afterward. During the lower Permian the gen- 
eral conditions were so much like those of the Pennsylva- 
nian that animal life was not materially affected. Gradual 
changes are observable in many directions, but the most 
notable feature was the rise of the reptiles, which began 
very soon after the amphibians appeared. This transition 
was through such slight differences that in some cases it 
can scarcely be determined where one order ceases and the 
other begins. Nowhere in natural history is the principle 
of evolution more clear and conclusive than in the fourfold 
progression from air-breathing fishes to the amphibians, 
from amphibians to reptiles, and later from reptiles to birds 
by one route and to mammals by another. 

VARIABLE CLIMATES 

It will be recalled that there are some indications of local 
glaciations in the late Proterozoic Age. These instances 
may be reasonably explained by regional elevations through 
internal disturbances, and thus afford very good evidence 



LIFE 139 

that the normal temperature relations of the sun and the 
earth at that period were not radically different from those 
of later times. The glaciation in the Permian, however, 
appears to have been of another character. In the Pleisto- 
cence the ice-sheets w r ere apparently more extensive in the 
northern latitudes, though not absent from the southern. 
In the Permian they appear to have been greater in the 
southern than in the northern hemisphere. More complete 
knowledge of the geology of these periods may show that 
these latitudinal differences were not so oronounced as 
hitherto supposed. 

If geology were without physical evidences of the changes 
in temperature, the fossil proofs and formations of organic 
origin would suffice. Thus it is known that during the entire 
Paleozoic and until the mid-Permian the climate of the 
earth to within ten degrees of the poles was mild and 
equable. The corals and limestones of the Cambrian, Ordo- 
vician and Silurian could not have been laid had the oceanic 
waters, north and south, been as cold as those of the tem- 
perate zones in the present age. That these conditions were 
not interrupted in the Devonian and Carboniferous is con- 
firmed by the vegetation. The land flora during the long 
course of its development before the Permian is fitly de- 
scribed as cosmopolitan, being composed of species common 
the world over. And this token of uniform climate is con- 
firmed by the structure of the wood : it was continuous and 
not made up of annual concentric layers, each the product 
of a season of growth followed by a season of repose. 

The cause of this constant and general climate has been 
the subject of as much speculation as the cause of the ice- 
sheets and with no more certain result. The solution, how- 
ever, has been aided by the abandonment of early theories 
advanced when the nature of the sun and its energies were 
much less understood. The physical logic would seem to 
point to a difference in the sun's radiation. The persistence 
of its great heat through geologic time, so long a mystery 
to science, is probably explained by the radioactive elements 



140 OUR WORLD 

in its mass. Yet there must have been some decrease, and 
the glacial epochs may well have been due to the accumu- 
lated effects of this expenditure, at length producing some 
degree of external obstruction. The warm interludes char- 
acteristic of both glacial periods are consistent with renewed 
outbursts of energy until equilibrium was finally established 
for another long ensuing stage, but with a somewhat reduced 
temperature. Coupled with this primary cause of climate 
was the probable change in the currents of the air and 
the oceans. Certain it is that in the early Permian culmi- 
nated in various parts of the world a series of mountainous 
upheavals and vast changes in the areas of the lands sub- 
merged. These new conformations must have profoundly 
affected the prevailing winds and oceanic streams. 

The consequences are first seen in South America and 
Europe, where the cosmopolitan flora vanished and new 
types appeared. In North America the conditions were 
somewhat different, but the changes were not less notable, 
owing largely to the arid or semi-arid climates that pre- 
vailed over most of the earth. Geologic time records no 
greater contrast in the character of the life of two successive 
periods than is revealed by the Permian and Triassic. Evo- 
lution had progressed so far and gained such momentum 
that changed conditions brought immediate and signal re- 
sponse. Although the Mesozoic Age was only half as long 
as the Paleozoic the evolution of life was far more rapid, 
vigorous and varied; and these characteristics are conspic- 
uous in the Triassic, with which the Mesozoic, the Age of 
Reptiles, opened. 

THE RISE OF MODERN TYPES OF VEGETATION 

The forests were soon transformed. All the more im- 
portant spore-bearing plants had gone, and the ancient ferns 
were merging into the modern stocks. The older seed- 
bearing plants had given rise to the conifers, from which 
the numerous family of evergreens have sprung. The Cycads, 



LIFE 141 

which were the ancestors of the great palm group, abounded 
in many regions. The forests, however, were not as exten- 
sive nor the trees so large as during the Carboniferous, 
except in favorable locations w T here the soil was well watered. 
In such places specimens have been found much larger 
than any from previous time. The uplands were not so 
well clothed, the vegetation there being of types adapted to 
the more arid conditions. In the swamps and moist low- 
lands the modified descendants of the Horsetails were the 
most abundant of the smaller plants. 

In the upper Triassic and during the Jurassic the climate 
again was warm. Marked seasonal changes had not yet 
been established except in extreme latitudes. The effective 
lowering of the temperature was in the polar regions and 
the waters. Thus in the Jurassic some kinds of vegetation 
became quite cosmopolitan. The floras of the world show 
no great changes, but a steady and gradual transition toward 
the modern types. This tendency becomes more clearly de- 
fined in the late Cretaceous, the close of the Mesozoic age. 
By this time the flowering plants, which had long been in 
their initial stages, were in the ascendant. Most of the 
now familiar woods of the temperate zones had taken the 
place of the former types, first appearing in the far north 
and thence spreading toward the interior latitudes with the 
moderation of the climate. Of decisive import to the course 
of mammal evolution, as yet only in its first stage, was the 
appearance of the sedges and grasses. With the physical 
logic so obvious throughout the entire course of evolution, 
when the flowers appeared the bees came also, beginning 
those mutual relations which have ever since continued with 
such beautiful effect upon the floras of the earth. The 
coloring of the flowers, however, must be sought in some 
other cause than the preference of bees and other insects, 
as was long supposed. These creatures are color-blind. To 
them all colors appear as shades of gray. Chemical rea- 
sons, through the property of absorbing only certain rays 
from the sun, are the probable explanation of floral hues, 



142 OUR WORLD 

without detracting from the aid of the bees in fertilization 
and diversity. 

CHANGES OF VERTEBRATE LIFE 

The development of animal life in some directions was 
so varied and so radical that a general outline will afford 
a better idea of its essential features than any attempt 
to group the details. In this era the marine invertebrates 
reached their climax. Many species became extinct, mainly 
because of the gradual cooling of the waters and the in- 
crease of superior foes. Others less complex were able to 
adapt themselves to the changing conditions, and their suc- 
cessors persist through variation. As the rise and fall of 
shelled genera serve the double purpose of illustrating their 
evolution and accurately marking the time, they have gained 
a prominence in both geology and biology more conspicuous 
than intrinsically important. From a practical point of 
view, the advent in the Jurassic of oysters and claims, lob- 
sters and crabs, is the most satisfying evidence of evolution 
among the many kinds of invertebrate life. 

The transition of vertebrate forms was naturally far less 
rapid and striking in the water than on the land. During 
the Mesozoic the principal fishes of the preceding age con- 
tinued, with some modifications and some change in their 
relative numbers. The sharks were still numerous, but less 
so than the ganoids, so called from their enameled and 
shining appearance. This great order originated early in 
fresh waters, but eventually gained predominance in the 
seas, which they held until the rise of the teleosts, or bony 
types, now comprising ninety-nine per cent, of all the fishes 
in the world. The teleosts appeared toward the close of 
the Paleozoic, afterward increasing steadily in number and 
variety, while the ganoids became correspondingly fewer. 
Of this ancient type only such species as the sturgeon and 
gar-pike remain. It was from the ganoid stock that the 
teleosts were derived. Because of this fact and the proba- 
bility that from the ancestors of the ganoids the amphib- 



LIFE 143 

ians had their origin, this great group holds an eminent 
position in the line of vertebrate evolution. 

THE AGE OF REPTILES 

The rise of the mammals from the reptiles, with all that 
implies, is not a more wonderful exhibit of the process of 
adaptation than that displayed by the evolution of the rep- 
tiles from such an unpromising source. Thus in a pecu- 
liarly suitable environment the first of the amphibians in- 
creased their power to breathe the air. Meanwhile through 
successive generations the fringe-fins were transformed into 
limbs and feet to aid in performing the new functions 
necessary to existence in new surroundings. With this start 
the subsequent changes were inevitable. The number of 
futile experiments made by nature to create the line that 
was to produce the primate mammals may be guessed from 
the many orders of amphibians and yet greater number of 
reptilian types, most of which are now extinct and the 
others hardly more than reminiscent of the period of their 
greatest development. The process was long and devious. 
From the first appearance of the fishlike creatures that led 
the way to the highly complex and gigantic monsters that 
marked the acme of reptile evolution nearly 20,000,000 
years elapsed. 

During the Reptilian Era of about 12,000,000 years eight- 
een great orders, each with many species, were evolved. Of 
these but five remain : the tuateras, a single form confined 
to New Zealand, the turtles, crocodiles, lizards and snakes, 
all in many forms. The snakes were the last to appear. 
They originated from a type which had lost its limbs; the 
diversity of species did not arise until much later. The 
other orders disappeared during the close of the Mesozoic. 
The almost abrupt extinction of such vast numbers in so 
many varieties, land and aquatic, from the very small to 
the largest creatures that ever inhabited the earth, is one 
of the mysteries of organic history. Extensive draining 
of the great inland seas during the late Cretaceous was 



144 OUR WORLD 

doubtless an important factor, involving prohibitive changes 
of habitat and the destruction of the normal food supply. 
The plant-eating species may have fallen prey to the car- 
nivorous. The eggs and young of both may have been 
devoured by the mammals that now began to multiply. Al- 
though the new-comers were yet small, they were equally 
voracious and vastly more alert and efficient in body and 
brain. Such are some of the explanations which have been 
advanced. The most probable cause was disease. 18 The 
reptiles had passed their physical climax and may have be- 
come subject to some world-wide epidemic such as destroyed 
whole orders of mammals over entire continents in later 
times. 

At this period the potential limits of evolution become 
apparent. Long before the intermediate forms of land 
vertebrates reached their culmination in the reptiles the 
marine invertebrates had passed through all the stages of 
their transition, and the surviving forms remain essentially 
the same as they were then. The marine vertebrates had 
a shorter course of development before the rise of the bony 
fishes, which mark the limit of their possibilities ; for their 
subsequent evolution has been only in detail of form and 
fitness. The amphibians were only a passing phase, and 
their distinctive career was correspondingly short. Such 
as still survive are but humble reminders of a bygone stage, 
provisional in its nature and inevitably merged in a higher 
development. The era of reptiles reveals similar character- 
istics, yet in a magnified degree. These uncouth creatures 
inherited the latent attributes of their amphibian ancestors 
and extended the inheritance in many directions until they 
also exhausted the physical power to proceed further, except 
by new and higher types of evolution moving through forms 
which had not become so specialized as to resist the change. 

The greater diversity of reptiles than of previous orders 
was due to the variety of conditions to which they could 
become adapted through increased flexibility of type. From 
probable lizard-like forms that may have originated in the 



LIFE 145 

Carboniferous the several great divisions arose and branched 
many ways. One or more of these divisions took entirely 
to the water, where they developed aquatic forms, some like 
fishes and others like serpents. Several varieties attained 
prodigious size and met the same fate that befell their con- 
geners of the land. Another division acquired very consid- 
erable powers of flight. From small bat-like creatures were 
evolved a numerous group of different shapes and charac- 
teristics, some being carnivorous and armed with formidable 
claws and teeth. Like birds, they had light skeletons with 
hollow bones. Specimens have been found with an enormous 
spread of wing, which enabled them to soar far over the 
shallow seas for prey of no small proportions. These flying 
reptiles were the most extraordinary of all extinct animals ; 
and curiously enough it was not from any of this group that 
birds were derived, but from an early branch of the original 
stem that produced the great order of the dinosaurs (ter- 
rible lizards). 

The earliest known bird is the Archeopteryx macrura, 
the imposing equivalent for "long-tailed primitive bird- 
creature." It was found in the Jurassic of Bavaria. The 
appearance of so highly developed a species in that early 
period shows that its lineage was as old as that of the flying 
reptiles, having diverged from the original reptile stock 
quite as soon and with a more promising future. Its reptile 
origin is unmistakable. Although with the legs, claws, feath- 
ered wings and general form of a bird, it retained several 
characteristics of the reptile. Claws extended from the 
second joint of the wings; the tail was a continuation of a 
long spinal column, at each joint of which was a pair of 
steering feathers, one on either side; and the jaws of the 
bony beak were well provided with teeth. There must have 
been a long series of intermediates of which no trace has 
yet been found. Even the long sequence from the Archeop- 
teryx to the next known bird fossils, from the Cretaceous, 
is entirely missing. Some thirty species of that period have 
been found in Kansas. They belong to two groups, one com- 



146 OUR WORLD 

posed of large water-fowl, some of them unable to fly, and 
the other of smaller ternlike birds also of aquatic habit. 
They show a distinct advance, though still bearing in their 
toothed jaws and other features the evidence of their rep- 
tile origin. Enough, however, is known to show that the 
varied evolution of later orders was well under way; and 
soon afterward, in the Tertiary, they attained the true char- 
acters of the modern birds. 

The precise mode in which the power of flight was de- 
veloped is yet the subject of debate among naturalists. The 
weight of the argument is probably with the theory that the 
beginning was batlike, all four limbs -being used and all be- 
coming more or less feathered. Physical necessity led to 
the evolution of the wings from the fore legs, which was 
aided by the original bipedal form of the species. The ef- 
forts exerted in attaining flight not only brought about the 
peculiar structure of the bones, but improved the circulation 
of the blood, which thus became warm, unlike that of reptiles 
generally. 

Were not the facts so well known from the abundance 
of fossils, which are yearly accumulating in the museums of 
the world, the weird variety of species and the magnitude 
of form attained by some of them would be incredible. Un- 
aided imagination could scarcely have conceived the uncouth 
shapes that inhabited the strange world of the Mesozoic. 
That great era of riotous growth in animal life, without 
other result in the climax than to produce the gigantic and 
the grotesque, is from a scientific point of view little more 
than an episode in which the possibilities of evolution in fav- 
orable conditions were carried to extremes. Lacking ele- 
ments of further adaptation to a changing world, most of 
these creatures passed into extinction, only leaving here and 
there a mighty reminder of a racial existence doomed from 
the beginning. 

The most significant fact of all this development of sheer 
physique is its independence of mind. No quadrupeds have 
ever lived upon the earth in which the brain has borne so 



LIFE 147 

small a proportion to the bulk of the animal. The great rep- 
tiles were mainly organized appetite, "complex mechanisms 
for the capture, storage and release of energy" without a 
nervous system of acute sensibility ; yet physically they have 
never been equalled. "As pure mechanisms, " says Osborn, 
"the cold-blooded reptiles exhibit as great plasticity, as great 
diversity and perhaps higher stages of perfection than the 
mammals. Nor does increasing intelligence favor mechanical 
perfection/' 

Most of the reptilian orders were oviparous, producing 
their young externally by depositing eggs which hatched 
without further care. Others were viviparous, producing 
their young internally. Both modes have survived in the 
reptiles of the present. The viviparous types appeared later 
than the birds, which have therefore retained their early 
character in this respect ; and it has been peculiarly suited 
to their entire evolution, though their vascular system was 
entirely transformed. 

The protracted time covered by the evolution of the rep- 
tiles from their amphibious origin is well illustrated by their 
e ggs> which are invariably laid on the land ; and the young, 
whatever may be the habit of the species, are air-breathing, 
while the amphibians always begin life in the water, breath- 
ing like the fishes by means of gills, which are soon lost and 
their office replaced by lungs. Thus the development of the 
tadpole rehearses within a few days the process of millions 
of years required for the transition from fishes to frogs. 

The evolution of the reptiles is similarly shown, though 
in a less distinct way, as with all high orders, by the embryo. 
The shelled egg, with the peculiar membranes that develop 
as incubation proceeds, to protect the embryo and provide 
for respiration, was as necessary to the first reptiles as their 
physical characteristics and was evolved at the same time 
through the same causes. The original stock was confined 
to the land and without doubt arose by reason of the arid 
conditions when they first appeared. The aquatic reptiles 
were a reversed evolution, appearing later through changes 



148 OUR WORLD 

in the habitat, but retaining their original character — the in- 
flexible rule with every order in which such a reversion has 
taken place. 

The change of the tadpole and the hatching of the chick 
have been of far-reaching import in the development of 
thought. They suggested and sustained the idea of evolution 
long before it was accepted by science. Some discerning 
minds saw in such phenomena sections of orderly growth 
from phase to phase and conceived, dimly but with assur- 
ance, that the organic world is a development. This was the 
solitary beam that shone through the long night of supersti- 
tion, the source of the worst evils that have beset the race. 
The science of embryology had a homely beginning, but it 
has been a potent factor of progress. 

THE RISE OF THE MAMMALS 

That the beginning of the most radical divergencies are 
usually the most obscure is again illustrated in the origin of 
the mammals. Such departures have been made only through 
a long series of minute changes during a long lapse of time ; 
and since only a very small proportion of any series has been 
preserved the entire process from stage to stage must be de- 
duced from fragmentary evidence of several kinds. It was 
long supposed that the original stock of the mammals 
branched directly from an amphibian because of certain 
peculiarities of anatomy; but the natural zeal of research 
to establish the true line of our own ancestory has made it 
clear that the pro-mammal was reptile. 19 The most important 
break in the line was finally closed by the discovery in the 
Triassic of Africa of fossil reptiles known as the cynodonts, 
because of their doglike teeth, which are distinctly incisors, 
canines and molars. While the structure of the head shows 
other mammal resemblances, the essential character of the 
order as reptiles is undoubted. This course of descent is con- 
firmed by two distinct types of existing animals that illus- 
trate intermediate stages of mammal evolution; the mono- 
tremes of Australia and New Guinea, the last survivals of a 



LIFE 149 

primitive egg-laying stock; and the marsupials, pouched 
animals such as the kangaroo and the opossum, which bring 
forth their young in an embryotic condition. 

The limbs of the African pro-mammals were also in an 
advanced stage of evolution, which enabled them to travel 
with ease and speed impossible to other reptiles. The power 
to migrate, associated with teeth adapted to different kinds 
of food, would indicate the greater degree of intelligence to 
be expected in the type representing the stock from which 
the ultimate evolution of form and brain proceeded. A wider 
range of habitat and food implies a greater power of obser- 
vation and choice. It is from this cause that the whole his- 
tory of the mammals is marked by specialized tooth struc- 
ture, in contrast with that of the reptiles generally, in which 
tooth development ceased. 

It is not evident that there was any relation between the 
disappearance of the great reptiles and the rise of the 
mammals. The mammals doubtless originated long in ad- 
vance of the geologic strata in which their fossils are first 
found. That epoch was probably the Permian, mainly be- 
cause of the climatic conditions. The cold and subsequent 
aridity forced animals to migrate or die. This travel in 
search of food in a different region improved leg develop- 
ment and increased activity. This in turn, through rising 
bodily temperature, transformed the cold-blooded reptile 
into the warm-blooded mammal. The change was attended 
by the development of the four-chambered heart and the 
complete separation of the arterial and venous circulation 
of the blood, and the increase of the temperature of the 
blood favored the evolution of a higher nervous system. 
Change of habit and physique tended to produce the 
placental mode of bearing the young characteristic of all the 
higher mammals. Changes of external temperature through 
emigration or seasonal causes tended to produce a protective 
covering. The birds gained feathers; and the mammals, 
hair. In such circumstances the animals that acquired these 
characteristics had the advantage; those which could not, 



150 OUR WORLD 

because too highly specialized, were in peril of elimination. 
Such is the rationale of mammal evolution. 

That the mammals, once started, spread with notable rap- 
idity is shown by the late Cretaceous in many different 
regions of the earth. These fossils are composed almost 
entirely of lower jaws, which, however, are the most sig- 
nificant part of the skeleton. They show that at the close 
of the Mesozoic the mammals were yet very small and of 
the most primitive types. Probably none of them were more 
than a few inches in length. That they were already di- 
versified is apparent from their teeth, which were adapted 
in each species to the particular class of food it required. 
This fact may well account for the exceptional variety and 
repidity of their evolution during the Tertiary, which now 
opened. Each type would thrive best where its peculiar food 
was most abundant, and, with great ease of movement, 
would seek it. Migration would lead to new habitats where 
the conditions, though favorable, were different. More- 
over, the mammals could more readily adapt themselves to 
circumstances than any of the orders which had previously 
existed, and their young were better protected. In such new 
situations there would be a tendency to evolution of form 
and character. These considerations are rather obvious, but 
they exhibit the factors of what the biologists are wont to 
describe as adaptive radiation. 

MAMMAL EVOLUTION 

In a sketch of origins the marvelous detail of the last 
phase of animal forms may only be broached. Upon this 
great subject some of the ablest minds of science have be- 
stowed their chief labors, and many of the successions have 
been worked out with a degree of completeness and cer- 
tainty that leave no problem as to the course of descent. 
The evolution of the elephant, the camel and the horse, not 
to speak of other types, as seen in the series of their 
skeletons, is so apparent that intelligent doubt is no longer 
possible. The sequences thus established are so many and 



LIFE 151 

so conclusive that they bridge every gap in every line of 
descent with the logical implication of a similar gradual de- 
velopment. One of the most suggestive episodes in the his- 
tory of thought is that at the time President Noah Porter 
of Yale was thundering against the principle of evolution, 
Professor Marsh, of the same college, was perfecting the 
now famous collection of skeletons, showing a complete 
series of forms beginning with a five-toed animal no longer 
than a fox from the Eocene and ending with a hoofed horse 
of the Pliocene. 

The duration of the Tertiary is generally estimated at 
about 3,000,000 years, divided among its four epochs — 
Eocene, Oligocene, Miocene and Pliocene. Of these the 
first is perhaps of most interest as being the evolutionary 
stage when the immediate ancestors of the modern mam- 
mals appeared. The initial stage, during most of the Meso- 
zoic, brought the mammals into being and laid the founda- 
tion for their future possibilities. This foundation was 
broad, and the possibilities included man. So well adapted 
were these orders to the conditions that were to endure for 
a long future that the divergence of the species progressed 
with greater speed than during any other period of organic 
evolution. And it is to be observed that the advent of the 
modern forms of animal life was long preceded by the climax 
of plant life. At no stage in the history of vegetation has 
its luxuriance and diversity been greater than during the 
close of the Mesozoic, when practically all of the present 
forms as well as many now extinct had reached their full 
development. 

Before the close of the Eocene the secondary and archaic 
types of the mammals began to die out and the more modern 
to take their place. This process is yet more striking in the 
Oligocene. Wherever the origin of the new types may have 
been, the phenomena of their diffusion is abundantly 
recorded. During some epochs there was a very general dis- 
persion of the land faunas of the several continents, with 
the exception of Australia, which was permanently severed 



152 OUR WORLD 

from Asia before the Eocene. At other periods whole orders 
dwindled away in one continent, while persisting in more or 
less modified forms in another. The land connection be- 
tween Asia and North America and between North and 
South America was inevitably followed by the intermigra- 
tion of the various faunas ; and the severance of those con- 
tinents invariably resulted in separate trends of evolution. 
This unity of North America, Europe and Asia prevailed 
during the Miocene and the Pliocene. Toward the close of 
the Pliocene communication between North and South 
America, which had been interrupted for more than a 
million years, was again restored. Thus the community of 
the mammalian life of most of the lands attained its greatest 
epoch in the early Pleistocene, just before the Ice Age. 

The vast importance of migration as a factor in animal 
evolution is aptly shown by the faunas of Africa and Aus- 
tralia. During the immensity of time covered by the de- 
velopment of vertebrate history a great part of Africa was 
exceptionally stable and in unbroken connection with Asia, 
which is supposed to have been the chief birthplace of the 
mammalian orders. It was also exempt from the ice sheets 
of the Pleistocene, which extinguished all life within their 
frigid advances. These circumstances have made Africa a 
more complete repository of faunal history than any other 
continent; yet there investigation has only begun. On the 
other hand, Australia, left to itself during the major part of 
mammal evolution, contained only the types which had 
evolved at the time of its isolation. When in modern times 
the first settlers entered that virgin country, placental 
animals did not exist there; its mammals were entirely of 
the egg-laying and marsupial species. It is therefore as- 
sumed that none of the original placental stock had ap- 
peared or at least had entered Australia when it was severed 
from Asia, and that the other types were already too highly 
specialized to lose their character. Madagascar affords a 
lesser but significant example of the faunal effect of isola- 
tion. It became an island before the close of the Tertiary ; 



LIFE 153 

and the subsequent history of its animal life has been plainly 
controlled by local conditions. 

The Age of Ice marks the boundary between the old 
world and the new. When at length the last glacial inva- 
sion retreated the aspects of life assumed an unwonted 
phase. The topography of the continents and their drainage 
systems were substantially the same as now. The newly 
established and somewhat lower equilibrium of the sun's 
heat had resulted in zones of temperature and seasonal 
changes as they now exist. The effect upon plant and 
animal life was decisive. The types of vegetation, which 
again advanced over the regions devastated by the ice, 
were in accord with the climates in which they grew; and 
the forms and distribution were essentially the same as 
now. 

With animal life, both land and marine, the sequel is more 
striking. Climatic changes wrought their immediate effect 
upon the faunas of the various regions, which thus became 
the abode of types suited to the varied conditions. This soon 
led to that localizing of species which has ever since pre- 
vailed. Birds and insects have since continued their evolu- 
tion to some extent ; but with animals, to use the word in its 
usual sense, the process has been arrested, except as it has 
been carried on by artificial selection. This arrest, however, 
has been because the conditions have been stable during the 
relatively short time that nature has been under intelligent 
observation. How far the extinction of types that existed 
in great size and numbers in the early Pleistocene has been 
due to man, who afterward emerged as the most formidable 
slayer the world has produced, cannot be known; but the 
human factor has been very great. Such mighty beasts as the 
mammoth, the mastodon,, the sabre-toothed tiger and the 
sloth, as well as the giant varieties of elk and bison, may 
well have reached their climax when man arrived with 
bludgeons, flint weapons and devices to quicken their ulti- 
mate doom. At all events, they gradually disappeared and 
their lesser relatives are most conspicuous in the menageries 



154 OUR WORLD 

and the exploits of the big-game hunters of the present gen- 
eration. 

In the seas the effects of altered temperature were like- 
wise manifested. During the Mesozoic the warm waters of 
the present temperate zones permitted a wide community 
of marine life in all its forms. During the cold of the Pleis- 
tocene all the warm-water life was banished to the tropics. 
The gigantic sharks, which had long been the scourge of the 
seas, disappeared utterly, and their smaller descendants are 
now confined to tropical waters and the warm oceanic 
streams. The teleosts, better able to adapt themselves to the 
lowered temperature north and south, gradually assumed 
their present status and variety. 

Quite as remarkable as the evolution of land mammals, 
has been the adaptation of many species to aquatic habits. 
It required about 10,000,000 years for the whale to evolve 
from a type similar to the existing tree shrew. And this in- 
stance is typical of the evolution of every other species of 
mammals, including man, as all have sprung from the same 
original stock. 

Such are the outlines of the history of life to the present 
time. Whatever may be the fundamental factors of evolu- 
tion and whether or not they may be discovered, the fact 
of this great process of nature is no longer open to rational 
doubt or debate. 20 



CHAPTER VI 
A PREHISTORIC PEDIGREE 

PRIMITIVE EUROPEANS 

IT HAS always been the lament of paleontologists that 
the record is incomplete. Nature itself rebels at the gen- 
eral preservation of the untold myriads of once living things, 
which perish and decay that their successors may live. Only 
here and there and now and then could fossils have been 
formed or preserved. Insects have been caught in liquid 
amber and held intact for ages. Everyone has seen the per- 
fect casts of creatures embedded in sediment that in course 
of time became stone. Some bones and wood that became 
fossils have lost their original character. The dead tissues 
were infiltrated with silica, lime or other mineral in solution ; 
the organic structure disappeared and the invading material 
hardened into the form it replaced. Fossils of human re- 
mains are few, especially those formed during the earliest 
stages of the race. The characteristics that made the race 
possible would have prevented the dead from being left in 
situations favorable to the preservation of the bones except 
in rare instances ; and the places where the oldest are most 
likely to be found have not as yet been searched. 

Direct proof, therefore, of the origin of the human species 
is wanting. If, however, the same kind of indirect evidence 
and the deductions from it that indicate origin are deemed 
conclusive as to other species, the origin of man is explained. 
Embryology and physiology demonstrate, as will be shown, 
that the physical evolution of man has proceeded in the same 
manner as with all the higher types of mammals and that 
there are no physical reasons why it has not been in re- 
sponse to the same organic laws. Moreover, the evidence 
of evolution since the species originated is so clear and con- 

155 



156 OUR WORLD 

elusive that all reasonable doubt has been removed. The 
proofs of organic change during any part of the career of a 
species is indirect evidence that the preceding processes 
were likewise an evolution. Such phenomena have appeared 
during the course of all orders. As there is no evidence to 
the contrary, evolution — whatever the causes — is regarded 
as the general law of organic development. 

The reason for the reluctance of many minds to accept 
the theory of the evolution of man from a lower order is 
seen in the character of the controversy after the theory was 
first announced. Darwin's Origin of Species was published 
in 1859; the sequel, which had been clearly foreshadowed, 
The Descent of Man, appeared in 1871. For several years 
attention to the subject was mostly confined to scientists; 
but the circle of interest gradually broadened until evolu- 
tion became a current topic in the press and on the platform. 
The theory was violently assailed. The acrimony of the 
attack was due to the radical challenge of ideas which had 
long prevailed for the most part in accord with theological 
doctrine. 21 The average mind, with such preposessions, was 
naturally shocked by the proposition that man evolved from 
a lower order of animals; that order, from one still lower; 
and so on down the scale. The theory, however, steadily 
won adherents by the weight of the evidence, which has 
greatly increased since Darwin's time, without any proof 
whatsoever to the contrary. To the leaders in science the 
evolutionary origin of man appears to be as certain as the 
evolution of birds from reptiles. The acceptance of this 
conclusion was of course aided by the prior geological proofs 
of the great age of the earth and the long duration and the 
progressive forms of life upon it. The first step was taken 
when the fact was established that man, as such, existed 
tens of thousands of years before the dawn of recorded his- 
tory in a stage of development far below the most inferior 
savage tribes of the present day. 

The most graphic and impressive evidences of the prim- 
itive phases of human evolution are fossil skulls and bones 



A PREHISTORIC PEDIGREE 157 

found at different times and in divers places. Fortunately 
for their preservation and study most of them were discov- 
ered during the period when their true significance could be 
understood. 

The earliest trace of man in Europe yet known was found 
in the sands of Mauer, near Heidelburg, Germany, in 1907. 
It consists only of a lower jaw, which, separated from the 
skull, had been carried with the sands of an ancient river- 
drift. The teeth are perfectly preserved and show con- 
clusively that the jaw is human; but other characteristics 
place the specimen at a low position in the human scale. 
Here, as with all such finds, geology completes the story. 
The enveloping deposit and other fossil remains found there 
fix the period of the "Heidelburg Man." He lived in the 
Second Inter-Glacial, about 375,000 years ago. 

Acute interest in the antiquity of man was revived in 191 1 
by the discovery of fragments of a skull shattered by work- 
men in an excavation at Piltdown, in Sussex, England. 
Subsequent search revealed the right half of a jaw, a canine 
tooth and a pair of nasal bones. All were in a good state of 
preservation ; but it is somewhat uncertain whether the jaw- 
bone belongs to the skull found or to that of another species. 
Near the specimens were deposited various other evidences 
— fossil bones and flint eoliths — that betoken their period, 
probably later than that of the "Heidelburg Man." They in- 
dicate a different branch of the human family, at a time 
when England was part of the European continent. It is 
significant that the main difference of opinion as to this skull 
among experts relates to its age, some maintaining that it is 
much older than the Heidelburg specimen. 

The next known of the human species, as to which much 
information has been gradually collected, is the Neander- 
thal race, so called from the discovery in 1856 of a skull 
and some other bones in the valley of that name on the 
Diissel River, Germany. As this was about the time the 
Darwinian Theory was put forth it started exhaustive study. 
At Gibraltar, twelve years before, a well preserved skull of 



158 OUR WORLD 

the same race had been found ; but so little was known of the 
circumstances and surroundings that its significance was not 
recognized, particularly as the origin of man was not then 
in controversy. In recent years a large number of skulls, 
skeletons and relics of the same race have been exhumed. 

The geological and other proofs of the age in which this 
race flourished, the physiological evidence of the stage of 
their development, the flint weapons and implements they 
made and used, together with the caves and other sites 
where they worked or dwelt, illustrate very completely the 
manner of life they led, the climatic conditions, the forests 
in which they roamed, the perils they encountered and the 
foods they ate. All these features have been minutely de- 
scribed by men who have devoted to the study a degree of 
discernment, ingenuity, and logic that compel the admiration 
even of those whom training and experience have qualified 
to analyze and weigh evidence in the most complicated trans- 
actions of modern life. 

Evidently the Neanderthal race appeared about 50,000 
years ago. Its superiority over human types that previously 
existed there, if we may judge by the "Heidelburg Man", 
enabled it to overrun at least western Europe during some 
two hundred and fifty centuries. It then in turn gave way 
to another and higher type, the Cro-Magnon, which through 
another long period evolved slowly improving methods and 
attained a higher plane of life. 

From the fact that the Cro-Magnons (so-called after the 
name of a place where remains were found) at the time of 
their appearance in Europe displayed a degree and quality 
of industry and art not possessed by their predecessors, it is 
manifest that they brought it from elsewhere. They mi- 
grated from Asia through northern Africa. Their physical 
characteristics were clearly Asiatic and not African and the 
trail of their migration is known. Their distinctive traits, 
physical and mental, and their great and advanced differ- 
ences from the Neanderthals indicate that Europe was not 
the seat of the origin of man or even of the early period of 



A PREHISTORIC PEDIGREE 159 

his evolution. With the early Cro-Magnons were members 
of still another distinct race. Skeletons of the so-called 
Grimaldi (from the name of the grotto where they were 
found), belonging to that period, are of a negroid and 
dwarf type. They are so strikingly different, from any other 
European type of that period, as to show an enormous lapse 
of time for their divergence from the original human stock. 
The Grimaldi in Europe were probably brought there from 
Africa by the Cro-Magnons. 

The ascendancy of this great race lasted for more than 
15,000 years. It was succeeded by several other distinct 
types, which had found their way into Europe from various 
quarters in the footsteps of their predecessors. 

If the stages of human development during these long 
epochs were disclosed only by skeletal remains, particularly 
skulls and jaws, the essential facts would be quite appar- 
ent; but they are also shown by another class of evidence 
quite as decisive, 

FLINTS 

Throughout the world human races and tribes in a prim- 
itive stage have used flint for weapons and other purposes. 
It was practically the only suitable material before metals 
were known. It was to be had in abundance, and it has sur- 
vived unchanged from the forms in which it was used. The 
variety and different shapes and styles employed during suc- 
cessive periods show improvement in skill and correspond- 
ing advance in mental capacity and habits of life. More 
kinds were needed, and they were better fashioned and 
adapted to the increasing uses to which they were put. 

The origin of flint is somewhat obscure ; but it is always 
found with deposits of chalk, where it was formed chem- 
ically. As limestones were originally similar to chalk forma- 
tions they frequently contain the same product, which, 
slightly altered in character, is termed chert. These facts 
account for the abundant supply of flint in most parts of 
the world. Much of France was submerged during the 



160 OUR WORLD 

Cretaceous, when most of the existing chalk deposits were 
laid. Thus flint in great plenty was ready to the hands of 
the early races that lived there. 

It was first used in the accidental but convenient forms 
(eoliths) in which they were found before skill was de- 
veloped to shape them into artifacts. Worked flints of the 
earliest type are termed Chellean, because they were first dis- 
covered at Chelles-sur-Marne. They are rude and but partly 
fashioned — eoliths with more or less work upon them to 
make them serviceable. They graduate downward to mere 
fragments without manual fashioning, such as were found 
with the Piltdown remains and elsewhere, and are thus 
known to be the form in which flints were first put to human 
use. There is no reason to suppose that the working of flints 
originated in one place and then spread by imitation. The 
use of eoliths would certainly not have so begun, and im- 
provement of them would have followed as a matter of 
course. The chipping of flints, therefore, was a common 
process taken up everywhere instinctively as soon as man in 
a primitive state attained intelligence enough to see the 
need. For this reason specimens of each of the several 
grades of shape and workmanship wherever found are quite 
similar and true to type, allowing for minor differences of 
technique and style that would be the normal result of local 
practice. 

The problem of the duration of the pre-Chellan period in 
Europe is of course identical with that of the rise of the 
human species in that quarter to the grade of the Neander- 
thals; and the estimates differ accordingly. Whatever the 
time, it must be measured by tens of thousands of years. 
The subsequent course of development to the age of metals 
is similarly gauged by the quality of the workmanship dis- 
played and at length by nascent efforts to represent objects 
by drawing and carving. This long process of development 
during what is fitly styled the Old Stone Age has been so 
fully established in all its aspects that the successive stages 
may be described briefly without reference to the numerous 



A PREHISTORIC PEDIGREE 161 

examples which have accumulated through many years of 
thorough investigation. These specimens have naturally in- 
creased in number in proportion to the improvement of con- 
ditions and mentality and the probable increase of the race 
during the later periods. 

The successive stages of workmanship on flints are the 
Acheulean and Mousterian of the Neanderthals ; the Aurig- 
nacian, Solutrean and Magdalenian of the Cro-Magnons; 
and the Azilian-Tardenoisian of the mixed peoples of the 
succeeding period to the beginning of the Neolihic Age. 
These names, as usual, are derived from places where im- 
portant exhibits were found. 

ACHEULEAN FLINT-WORK 

In the Acheulean period the camps of the flint workers 
were usually on open ground, where the soil blown by the 
winds afterward covered and retained the evidence. The 
stations were near the supply of materials and therefore in- 
dicate that they were chosen for the preparation of flints 
rather than for habitation. Some stations were frequented 
for that purpose during the entire paleolithic age by suc- 
cessive races. At the grotto of Castillo, in northern Spain, 
deposits many feet in thickness accumulated. They formed 
so many characteristic strata that they present an epitome 
of the flint industry of western Europe from Acheulean 
time to the Age of Bronze. The stations are very numerous 
in Italy. In France, thirty are known, besides others in 
Portugal, Spain, England, Germany, Austria and Poland. 

The workmanship throughout the period was very uni- 
form. It was much more skillful than the Chellean, and the 
forms were more symmetrical. Toward the close of the 
period there was a marked improvement in technique, some 
of the smaller implements being very superior. Also the 
increased number of forms shows a greater diversity of 
uses and a corresponding advance in the qualities of the 
users. 

There is no indication that the Neanderthals then lived 



162 OUR WORLD 

in caves or sheltered places. They were doubtless nomadic. 
This appears from the character and uniformity of their 
flints wherever found and may be implied from the genial 
climate that prevailed over the regions they inhabited during 
this period. 

The climatic conditions supply important data in cor- 
relating the facts of human evolution in Europe with the 
results of recent researches elsewhere and should be borne 
clearly in mind. 

The second glaciation was much the greatest of the four 
principal phases during the Ice Age. The race represented 
by the "Heidelburg Man" lived in the long interim between 
the second and the third glacial periods. The latter is sup- 
posed to have begun about 120,000 years ago, and the period 
of advance and retreat to have lasted about 20,000 years ; 
but the extent was much less than that of the second. The 
Neanderthals appeared in the succeeding inter-glacial stage, 
which began, according to the most generally accepted esti- 
mates, about 100,000 years ago. The Chellean and Acheulean 
flint-workers lived in a climate more genial than that of to- 
day in western Europe. 

Toward the close of the Acheulean the conditions began 
to change. The fourth glaciation had begun. Although it 
was less extensive than the third, the consequences to the 
flora and fauna of western Europe were profound. The 
glacial accumulations centered in Scandanavia and the Alps, 
from which there were two very similar advances, the reces- 
sion between being only partial. At first the climate became 
cool and dry, except in the immediate vicinity of the ice. 
Afterward lower temperatures and great dampness pre- 
vailed, with some moderation between the two glacial ad- 
vances. The final recession ended not less than 20,000 years 
ago. During the cold seasons the inhabitants were driven to 
shelter. The flint-workers who continued their employment 
sought the protection of cliffs and the entrances to caves. 
The first evidence of the use of fire is found in charred wood 
and bones among deposits at the sites of the flint industry. 



A PREHISTORIC PEDIGREE 163 

THE MOUSTERIAN 

The beginning of the new conditions brought on the 
Mousterian period. The late Acheulean was the climax of a 
gradual but steady improvement in the workmanship of the 
Neanderthals beginning at the close of the Chellean. Dur- 
ing the Mousterian the quality of the work is usually in- 
ferior and its character distinctly different. The technique 
is good, but it shows less attention to form and detail. In- 
dustry in general showed no progress or invention. The 
principal change was the use of flakes of flint flat on one side 
to save work on the other. Some old types of implements 
were abandoned and new ones were made for other pur- 
poses, due to changes in the conditions of life. The cold 
climate compelled the use of skins for clothing, and to pre- 
pare to fasten them together required other tools. 

The places of abode of such as remained in the old habitus, 
apparently caves for the most part, supplied but little com- 
fort. Even through the dryest seasons the collected mois- 
ture trickled down the walls. The condition of the vertebrae 
of both animals and human beings of that period often 
shows signs of swelling and inflammation caused by long ex- 
posure to the damp. Crowding in caves and shelters tended 
to reduce the vigor of a people which had always lived in the 
open. As might be expected from such conditions, the be- 
ginnings of superstition are seen, for there are traces of 
primitive religious ideas and ceremonial. Yet this folk were 
brave and hardy. Weaklings must soon have perished. Only 
the fearless and sturdy could have captured or killed the 
mighty animals upon whose flesh they subsisted. It is signi- 
ficant that there are nearly as many known Mousterian sta- 
tions as there are Acheulean. 

The rigor of the climate at the maxima of the fourth gla- 
ciation and the changed conditions of human life may be 
inferred from the revolution of species, both plant and 
animal, of the regions affected. In place of the subtropical 
fauna known to the Neanderthals of the previous period 
now roamed the mammoth, the wooly rhinoceros, the rein- 



164 OUR WORLD 

deer, the musk-ox, the arctic fox and many other species 
characteristic of a cold habitat, many being now extinct. 
Corresponding vegetation replaced the copius and fruitful 
growths which could no longer exist there. These transfor- 
mations must have radically affected the former type of hu- 
man beings that dwelt there and checked their further de- 
velopment. This conclusion is enforced by like phenomena 
too often seen in biological history to admit of doubt. That 
the Neanderthals should have yielded to a superior race 
when it came from the south after the untoward conditions 
had begun was inevitable. The arrival of Cro-Magnons 
marked the beginning of a new epoch. 

THE CRO-MAGNON RACE 

The Cro-Magnons were physically as fine a race of hu- 
man beings as ever existed. They were of great stature, 
straight and well proportioned, with large and nobly 
modelled skulls. With them the brain had reached the 
climax of capacity. Within the limit of that capacity lay the 
future of the human species. It is not to be supposed that a 
race appearing at that time could have reached such phys- 
ical perfection without corresponding antecedents dating far 
beyond the Acheulean period. If that be true, the Heidel- 
burg, Piltdown and Neanderthal races are merely proofs of 
stages through which the ancestry of the Cro-Magnons had 
passed long before. 

It is quite certain that this type appeared in Europe be- 
tween 25,000 and 30,000 years ago. The disappearance of 
the Neanderthals was abrupt and complete. They were prob- 
ably exterminated. They were no match for an enemy large 
in number, more powerful in body and mind and armed 
with better weapons. There is no evidence that the Nean- 
derthals had the bow and arrow, which the Cro-Magnons 
doubtless possessed then as they did later. The inferior race 
was probably disdained by the conquerors, as there is no in- 
dication of an intermingling of blood. 

The Cro-Magnons were chiefly of nomadic habit, to which 



A PREHISTORIC PEDIGREE 165 

they were perfectly suited and in a favorable environment, 
yet their employments were far more diversified than those 
of their predecessors, as appears from the great variety of 
weapons, tools, implements and ornaments made and used 
by them. The Neanderthals were without an esthetic sense, 
a distinct trait of the Cro-Magnons and later developed to a 
marked degree. The burial customs of both races were so 
similar that they may be regarded as normal primitive tokens 
of regard for the departed : weapons, implements, ornaments 
and food were interred with the dead. 

As the advent of the Cro-Magnons in Europe was during 
the final phases of the glacial period the climate had already 
improved, and it gradually became much the same as that 
which now prevails there. Plant and animal life responded 
to the change. Yet the change was not the restoration of 
former conditions. The close of the Ice Age, as already 
shown in another connection, marked a transition from the 
old world to the new. Many previous forms of life gradu- 
ally but entirely vanished, while the descendants of others 
underwent more or less modification. Many species mi- 
grated thither from regions which had not been directly 
affected by the ice. Natural forces in a changed environ- 
ment likewise reacted upon the human species that dwelt 
there. All this is clearly shown by specific evidence. 

A considerable time elapsed before the moderation of the 
climate allowed the Cro-Magnons to pursue a more free and 
improvident course of life in the open. The summers slowly 
became warmer, dryer and more stimulating, though the 
winters were still severe. Caverns and other natural shelters 
were needful during the inclement seasons. The habitations 
and flint-stations used in former times were taken over. 
Not until much later did the salubrity of the climate permit 
the use of open stations and the more scattered dwelling 
places and variant modes of life apparent from the many 
vestiges of that age. As the huge animals of the Mousterian 
dwindled away and finally vanished the more modern fauna, 
including great herds of wild cattle and horses, made their 



166 OUR WORLD 

appearance. The effects of these changes upon human de- 
velopment in that region might be inferred; but they are 
attested in the most graphic manner by the tangible proofs 
of cultural development. 

THE AURIGNACIAN ARTS 

The stages of Cro-Magnon culture are distinct and char- 
acteristic. The first (Aurignacian) is much superior to 
Acheulean achievement, though still primitive. Perhaps the 
fact of most significance is shown by rude sketches of huts 
or shelters made of logs and covered with hides. These 
dwellings were evidently located at points most convenient 
for hunting and fishing, in a country where game of many 
kinds abounded. The building of these shelters was doubt- 
less the first architectural practice in western Europe. 

The art impulse was strong and evidently general. That 
it was natural to them is seen in the early and rapid process 
of its development, especially in attempts to picture the 
animals most familiar to them. These sketches begin with 
crude efforts to represent the huge creatures yet in the coun- 
try when the Cro-Magnons arrived, then of others that suc- 
ceeded. The quality of art thus initiated is strikingly pro- 
gressive. Attempts in color were often made, the pigments 
being mixtures of ochre, manganese and other common in- 
gredients. Besides these essays at mural painting, modeling 
in the round was undertaken. Quite naturally it is the 
female form that is represented ; and if the corpulence com- 
mon to most of the figures shows a sedentary life the women 
were favored in the activities of the time. Carving on stone, 
bone and ivory was practiced, with some taste and dexterity. 
Staffs and wands, made from deer antlers, apparently for 
ceremonial use, and also bas-reliefs and incipient sculpture 
are among the exhibits of Aurignacian art. From construc- 
tion to decoration is a natural and easy step. 

It is to be inferred from all these interests and employ- 
ments that the making of the necessary tools and imple- 
ments was in itself a very considerable industry. The in- 



A PREHISTORIC PEDIGREE 167 

crease in the number of stations and the wider territory in 
which they are found show not merely the greater volume 
of the industry, but a probable growth of population. Not 
only is the workmanship finer than that of the Acheulean, 
but manifestly of different origin, as might be expected of 
a more highly developed people from a source where in- 
dustry had long been in an advanced stage. The artistic 
traits displayed by the earliest Cro-Magnons could have been 
evolved only by a protracted period of practice among their 
antecedents. The many kinds of small articles of personal 
adornment found with and upon buried remains point to 
customs so general as to require a vast time for them to be- 
come an ordinary detail in the life of a people even at that 
stage. Nor were these traces of the Aurignacian confined to 
western Europe. They girt the Mediterranean, and evince a 
variety of style and origin that could have come only from 
invention in many places and wide imitation. 

THE SOLUTREAN 

The chief method of workmanship on flint during the 
Solutrean epoch, which followed, is so different from that 
employed during the Aurignacian and appears so abruptly 
as to show an independent origin. The so-called "Solutrean 
retouch" was executed by pressure which removed thin, fine 
flakes, thus producing sharp edges and perfect symmetry. 
The barb now appears for the first time. The products of 
this technique mark the climax of the Solutrean flint in- 
dustry ; and they are due to the speedy adoption of a new 
method because of its manifest superiority. Of course such 
a method might have been discovered by expert workers ; 
but other facts point to a foreign influence. These facts 
bear strongly on the problem of the source from which all 
the human species radiated. 

The Aurignacian technique was far more widely spread 
than the Solutrean, which is found nowhere else around 
the Mediterranean. It doubtless entered Europe from Asia 
directly and not through northern Africa. This conclusion 



168 ' OUR WORLD 

is supported by the appearance at this time along the Danube 
of a race distinctly different from any which had previously 
inhabitated Europe, so far as yet known. This race (The 
Brunn) was by no means equal to the Cro-Magnons in gen- 
eral capacity, but it had somehow acquired the best method 
of working flints. This advantage appears to have been ap- 
preciated by their neighbors, who soon brought it into com- 
mon use, for no remains of the Brunn race have been found 
in France. 

The progress of art in the Solutrean was not equal to that 
of the flint industry, yet on the whole the quality was sus- 
tained. Specimens of both linear and plastic forms are 
numerous, and a beginning was made in animal sculpture. 
Quite elaborately engraved implements of reindeer horn are 
characteristic of the period. It may be assumed that more 
attention was paid to clothing, as well-made needles of bone 
neatly pierced at one end have been found, and the like were 
doubtless in common use. Indeed, bone had already been 
substituted for flint in many tools and ornaments. 

THE MAGDALENIAN 

The Magdalenian closed the long career of the Cro-Mag- 
non race. The beginning of that epoch is assigned at not 
later than 16,000 B.C., the combined duration of the Aurig- 
nacian and Solutrean having been about 9,000 years, ac- 
cording to the estimates most generally accepted. The epoch 
lasted about 6,000 years. During that time climatic changes 
materially affecte'd the conditions of life. After the period 
opened there was another glacial advance from the same 
centers as before. It was less extensive than any previous one, 
yet severe enough in its effects to leave unmistakable traces 
in the remains of plant and animal life then existing within 
the range of its influence. The ice then retreated and former 
conditions were renewed. Later, toward the close of the 
Magdalenian, the process was repeated with like results. It 
was during the interval of the two glacial advances that the 
culture of the epoch reached its highest development. 



A PREHISTORIC PEDIGREE 169 

Flint was still used for many ordinary purposes, but those 
purposes were as well served by rougher workmanship. 
Wherever practicable bone, horn and ivory were substituted, 
and they were better materials for artistic treatment, which 
accordingly progressed. This phase of Magdalenian art and 
industry is very prominent. The use of bone implements led 
to several kinds of barbed javelins for the hunt and harpoons 
for spearing fish. As these harpoons now first appeared it 
may be that interest in the chase was divided with fishing to 
a greater degree than ever before. The mere variety of 
weapons, implements and utensils suggests the many differ- 
ent activities that mtist have arisen; for most of them re- 
quired such special skill that they could not have been gen- 
eral. The fact implies ranks and occupations more or less 
distinct and recognized. It is not surprising, therefore, that 
among such people the natural promptings of their alert 
intelligence should have struggled for artistic expression in 
every primitive form and applauded its exercise. Crude and 
fragmentary as these efforts were in drawing, graving, 
modeling, sculpture and even painting, they display with un- 
answerable force the process of mental evolution through 
which the highest intellectual faculties began their ascent. 

From the variety of shells and other objects used for orna- 
ment and drawn from many different and remote places it 
is possible that there was some system of barter and com- 
munication. The tribesmen must have wandered far and 
wide and returned with the results of their primitive trade. 
There are no indications of battle or conquest. At the 
height of their dominance the Cro-Magnons were spread 
throughout central and western Europe. They had no rivals 
and absorbed no streams of incoming alien blood. Their 
rule was distinctive and their culture was their own. What- 
ever their achievement owed to external and intrusive ideas 
and customs, the foreign factors were subordinated to the 
native or moulded into harmony with them. The Magda- 
lenian culture was not Mediterranean; no stations are 
known in those regions that show either the origin or the 



170 OUR WORLD 

influence of its distinctive features. When the epoch drew 
to a close that mighty race was approaching extinction, 
except as its blood was mixed and diluted with that of its 
successors. The cause of its disappearance is unknown, 
though there is some evidence of physical and mental de- 
cline. It had probably passed through a cycle of existence, 
like so many other races before and since. 

THE CLOSE OF THE OLD STONE AGE 

The disappearance of the Cro-Magnons was quite as 
abrupt as that of the Neanderthals and almost as complete. 
A small and decreasing number lingered in southern France 
and northern Spain; but even these eventually died out, 
leaving no descendants. All their distinctive traits vanished 
with them. Their successors, of several different races and 
types from different quarters, were at least alike in their 
lack of artistic tendencies. For them sheer existence ap- 
pears to have been the sole object of their efforts. Yet 
they were not such mighty hunters as the Cro-Magnons, 
who enjoyed the excitement of the chase. Fish and veni- 
son were apparently their staple foods. They were rough- 
and-ready barbarians ; and their weapons, tools and utensiL 
were designed for use and not for ornament. There are 
some indications that war was a condition of the time. Hardy 
and savage tribes with different speech and traditions must 
have come into collision. An environment of hostility and 
danger would thus account for the rude and inartistic qual- 
ity of the industrial remnants of the Azilian-Tardenoisian 
epoch, which closed the old Stone Age in Europe. 

The epoch ended about 7,000 B. C. The climate had 
been cool and moist, and the inhabitants generally lived in 
grottos, caves and sheltered places. Vast forests covered 
much of the continent. The rivers and streams abounded 
with fish, a great variety of edible game roamed the goods, 
and herds of deer, wild cattle and horses ranged the plains. 
If there were races of men from other regions where the 
increase of numbers had decreased their resources and op- 



A PREHISTORIC PEDIGREE 171 

portunities they would have migrated to other scenes where 
life held greater promise. That course was followed so 
often in after times as to cause some of the most tragic 
events in history. The evidence is conclusive that such 
migrations occurred in paleolithic times. Toward the end 
of that age such causes operated to an increased degree. 
Hordes from the congested East debouched into the rich 
and alluring wilderness abroad. Western Europe thus be- 
came the terminal region of these migrations until Colum- 
bus opened the way to the New World. 

Although rude and inartistic, the invading races were by 
no means backward in mental capacity. They lacked taste 
for ornaments, but they had pots and kettles and had some- 
where gained some knowledge of metal. They were an- 
cestors of races that inhabit Europe and America to-day. 
It stands to reason, therefore, that the development of the 
brain and knowledge possessed by their antecedents took 
place elsewhere than in Europe and extended to a period 
far more remote than that to which the earliest European 
races belong. 22 

PRIMITIVE MAN IN THE NILE VALLEY 

The Stone Age of Europe, together with the natural his- 
tory of the anthropoids, has hitherto been the basis of all 
speculations as to the origin of man. The ablest investi- 
gators of those races, however, have more and more tended 
to the conclusion that the history of the first Europeans 
is that of an evolutionary phase too late to disclose origin 
except as illustrating the general law that applies to origin 
as well as to subsequent evolution. Recent researches in 
another region have thrown a new light upon the whole 
subject. 

The human races that inhabited Europe during the Paleo- 
lithic Age contended with disadvantages not suffered by 
other human races in regions not materially affected by the 
severe conditions of the Pleistocene. The progress of the 
Neanderthals and the Cro-Magnons was repeatedly stayed 



172 OUR WORLD 

by advances of the ice. The total time of these obstruc- 
tions covered many thousands of years. In a different envi- 
ronment where the momentum of progress was not arrested 
by such conditions we should expect to find proofs of a 
much earlier evolution of mind than could have been pos- 
sible in Europe ; and we should expect to find them in the 
regions where the earliest civilizations appeared. Egypt 
and Mesopotamia being such regions, the origin of their 
cultures was probably not far from those natural centers. 
Whatever may be the results of future investigation, enough 
has already been learned as to the course of evolution in 
Egypt to disturb any idea that the Heidelburg and Nean- 
derthal races were the earliest in fact instead of being 
much later representatives of types which had existed else- 
where very long before, and also to discredit any alleged 
evidence that a distinctly pre-human species has been 
brought to light. 

During the entire Ice Age in Europe what is now Sahara 
Desert was a fertile country with abundant rainfall. It 
became a desert in later times. There has been no change 
of mean temperature there in several thousand years The 
cause of the change to desert conditions is thought by some 
to be the rise of dunes along the Soudan, which gradually 
lessened and finally prevented the rainfall. Be this as it 
may, paleolithic man thrived there during the period of 
the Heidelburg race, with a flint industry as far developed 
as the Chellean. But it was the region of the Nile that 
supplied the most ideal conditions for human evolution. 
This was in part the result of a peculiar geologic event. 

During the time when the lower levels of the later Plio- 
cene were formed the coast line of the Mediterranean was 
as far south as the present site of Cairo. Two fractures, 
varying from 4 to 15 miles apart, then occurred through 
opposite sides of that place and extended southerly for some 
400 miles. They produced what is known as a "block fault." 
This block between the two fractures in the Eocene lime- 
stone sank about 800 feet, forming a trough afterward 



A PREHISTORIC PEDIGREE 173 

prolonged by other displacements to the site of Gebelen, 
about 450 miles from Cairo. Into this trough the sea en- 
tered for a distance of 90 miles. Here was the first mouth 
of the Nile later on, perhaps in the period of the European 
First Inter-Glacial. Streams produced by the extraordinary 
pluvial conditions of the time poured into the depression. 
Sediments and detritus on the bottom were swept along by 
the current until they dammed the discharge of the water 
into the bay. A lake or a series of lakes was thus formed, 
lasting for several thousand years until the Nile originated 
and broke through. This situation made possible the most 
remarkable development of its kind in the world. 

In the course of time the bottom of the lake was covered 
with conglomerate masses of gravels, marls and limestones, 
and terraces of limestone and indurated gravel were built 
up along the sides. The fossils contained in these deposits 
show that the period of their formation corresponds with 
the late Pliocene and early Pleistocene. After the Nile 
forced the barrier and drained the lake much smaller ter- 
races were formed of mud, sand and fine gravel, rising in 
gentle slopes along the edges of the land that has been 
the ribbon of cultivated soil in Egypt from prehistoric 
times. The depth of the river deposits, which form the 
present alluvial floor of the Nile Valley, ranges from 30 
feet at Thebes to 130 feet in the Delta. So deep an accu- 
mulation could not have been possible in the relatively 
short time since the close of the Pleistocene. According 
to the present estimates, therefore, the lower half of the 
mixed clays and sands that comprise so much of the Nile 
alluvium was laid concurrently with the period of the Fourth 
Glacial. Nowhere in any of these deposits, lake or river, 
have been found any evidences whatever of a fauna char- 
acteristic of the glacial conditions of Europe. On the con- 
trary, buffalo horns, and teeth of the elephant and the hippo 
have been exhumed. Even the lake marls of the Fayum 
have yielded teeth, hoofs and leg-bones of the horse, and 
also the mandible of a man! There can be no reasonable 



174 OUR WORLD 

doubt that the period of the lower river alluvium corre- 
sponds to the Fourth Glacial. That fact established, the 
provisional hypothesis advanced by Breasted as to the time 
division of the preceding formations seems warranted : the 
lacustrine deposits took place during the late Pliocene and 
the First Glacial ; the upper river terrace, during the Second 
Glacial ; and the lower, during the Third Glacial. Whether 
or not this correlation be finally established, other proofs 
show conclusively that human development in the Nile Val- 
ley was far in advance of that in Europe at all the early 
stages. 

During this immense lapse of time the Sahara plateau 
was habitable, and from the discoveries already made it 
seems probable that men able to produce flint implements 
dwelt along the foot of the cliffs above the lake near the 
present site of Thebes during the period of the First Gla- 
cial in Europe. Many rude artifacts made by these men 
appear to have been swept from the shores intc the lake, 
where fhey were found in the lacustrine terraces 50 feet 
or more below the alternate strata of those formations. 

Along the crest of the cliffs just above Thebes are sta- 
tions where flints were fashioned at a very remote period. 
When the lake was drained and the Nile current began 
to flow through the bed the heavy erosion of the pluvial 
period carried great masses of rock debris into the valley. 
Of this the upper river terrace was in part formed. Many 
of the flints that lay on the ground were carried away by 
the movement and are now found embedded in the terrace. 
The conglomerate materials of the formation manifestly came 
from the neighboring heights, and the flints found within 
it are of the same type and workmanship as those still 
found there. The conclusion is obvious. 

The river was then from 45 to 60 feet above its present 
highest level. As its volume decreased (probably during 
the period of the Second Inter-Glacial) the people began 
to shift into the valley, transferring their work stations 
to the terrace, where some of their implements have been 



A PREHISTORIC PEDIGREE 175 

found. In front of the cliffs are scattered the hearths of 
this primitive folk; and here, it is not unlikely, wattle 
huts were built somewhat later. On the convenient rocks 
of the cliffs the aboriginal artist amused his hours of idle- 
ness by scratching the forms of animals he had hunted, 
for these drawings belong to this stage of Egyptian life, 
at a time when the Neanderthals were only beginning their 
career in Europe. They had learned to build floats of reeds 
for crossing the river, and these were soon displaced by 
wooden boats, which are also pictured on the cliffs. 

As the waters of the Nile receded the dwellers on the 
banks followed until the river had sunk to its present level. 
It was not until the Fourth Glacial in Europe that the 
river began the annual overflow and deposit of alluvial 
soil. When this phenomenon appeared the dwellers upon 
the spaces overflowed withdrew to higher ground. The 
process of this inundation is known to have been gradual 
until it reached the maximum spread which has been an- 
nually repeated with great constancy during historic times. 
As the alluvium slowly widened it buried the vestiges of 
life that were not removed. Thus in the neighborhood of 
Thebes such relics are covered to a depth of 30 feet. Buried 
there, it may be assumed, lie many of the proofs of the 
successive phases of progress to a degree of civilization 
known to exist at the beginning of the pre-dynastic history 
of Egypt. 

If nothing were known of the vast interval between the 
early settlements along the Nile at the beginning of the 
Fourth Glacial and the close of the Paleolithic Age of Eu- 
rope, the course of human evolution in the Nile Valley 
could be very accurately discerned. The emergence at that 
time of conditions denoting a relatively high degree of 
civilization would attest an unbroken and steadily acceler- 
ated development of industry, agriculture, trade, art, society 
and government. These conditions could not be explained 
otherwise. But there are proofs, direct and indirect, of 
facts that have no other meaning. 



176 OUR WORLD 

EARLt PROGRESS OF THE NILE PEOPLE 

The entire region was free from the rigorous and change- 
able climates that prevailed in Europe. There were no con- 
ditions that checked or abated the course of development. 
During the thousands of years when the human species in 
Europe were struggling with adverse conditions and leading 
a precarious life in conflict with fierce and formidable beasts, 
the Egyptians enjoyed a salubrious climate and freedom 
from the hardships and dangers of the European wilder- 
ness. There were no causes in nature to retard their prog- 
ress ; and that it was not retarded is shown by early tombs 
and the Pyramids, erected by a highly organized commu- 
nity far advanced in development when the barbarians of 
Europe were still in their Neolithic Age. 

From borings made north of Cairo it has been determined 
that the average rate of alluvial deposit during the last 4,000 
years has been about 4 inches per century. It was probably 
less at first and increased very gradually. These borings 
found pottery at a depth of nearly 60 feet. This shows 
that the time when the pottery was left there was from 
15,000 to 18,000 years ago, more probably the latter. If 
the inhabitants at that age generally used such pottery — 
everywhere one of the first proofs of development beyond 
sheer savagery — their progress in other respects must have 
corresponded, for these vessels are of various kinds, orna- 
mental as well as useful. 

Already the causes that made the Sahara a desert had 
begun to act, and the rainfall in Egypt was gradually dimin- 
ishing. This would have compelled the dwellers in the 
valley to depend more and more upon the annual overflow 
of the Nile as the main source of their welfare. At that 
period, therefore, the rank growths along the alluvial banks 
were removed and the beginnings of a regular agriculture 
were made. The grasses from which the cereals have come 
were cultivated, animals were domesticated and other forms 
of industry and consequent trade began. These phases of 
development are as yet deductions, but from fundamental 



A PREHISTORIC PEDIGREE 177 

facts that make them presumptively valid. Moreover, they 
are confirmed by another class of evidence not less cogent. 

Since the arable land was limited it would have been 
used less and less for the burial of the dead. During the 
period when the alluvium advanced, burial places previ- 
ously nearby would have been covered. At length the dead 
would have been interred on the terraces out of the way 
of living. Excavations have not yet been made in search 
for these supposed burial places ; but the earliest cemeteries 
known are upon the higher ground opposite the alluvium. 
These cemeteries have been quite thoroughly investigated, 
and though they do not extend actual knowledge to the 
purely Neolithic Age of Egypt, the period when the prob- 
able burials occurred and the cultural conditions assumed 
to have then existed are in accord with the theory of prior 
gradual progression. 

These interments were made not later than 4000 B. C. 
The flint workmanship found there is unsurpassed anywhere 
in the world at any time. The "ripple-flaked" knives, for 
example, are so perfect in symmetry and so exquisitely 
fashioned that they must have been made by craftsmen who 
delighted in their skill. Yet the flints are merely incidental. 
As shown by other articles interred with the dead, the 
making of pottery, which had started long before, had been 
developed to a fine art. The many kinds for various uses 
point to a great industry carried on by expert artisans. 
Much of the pottery was made from the clay sediment of 
the Nile shaped and baked in regular forms. Circular pots 
and vases show the use of the potter's wheel; and their 
decoration, the combined result of craftsmanship and taste. 
Some forms have black tops, while others are of polished 
red with white, brown or black lines incised. Vessels of 
stone, bored and finely worked by hand, likewise betoken 
the advanced state of the stone-cutter's craft. There also 
abound specimens that display the varied means employed 
for personal adornment, such as bracelets, rings, combs and 
hairpins of ivory and palettes of slate for mixing face-paint. 



178 OUR WORLD 

More significant are the evidences of textile skill. The dead 
were laid on mats of woven reeds bound with flaxen cord. 
Some of the bodies were wrapped in a sort of linen cloth, 
by far the earliest known. That linen represents a culture 
of flax which must have begun along the Nile very long 
before. 

Nor w r as that culture exceptional. From the remains of 
those early dead and in jars buried with them the grains — 
barley, millet and wheat — then used for food have also been 
found. The originals from which these grains were pro- 
duced still grow wild in western Asia. All the varieties 
of wheat have sprung from emmer, which these dwellers in 
the Nile valley had already improved to a high degree. 
The domestication of animals and water fowls at that period 
has not been demonstrated by actual proofs; but it may 
fairly be inferred from the state of agriculture. All the 
details of the practice are shown at a somewhat later period 
on the pre-dynastic reliefs. 23 

THE PROBABLE SEAT OF HUMAN ORIGIN 

Whether or not northern Africa was the scene of the 
origin of man, the evidence now at hand (though the real 
investigation has only begun) clearly indicates that it was 
the seat of the earliest development of the human mind. 
In any event, it is apparent that the natural history of early 
man in Europe presents a local phase and not the original 
development. If the chronology of that history to the 
Mousterian, in the middle of the Third Inter-Glacial, were 
disregarded, and the duration shortened at least one-half 
to allow for the retarding effects of the first, second and 
third glacial periods, it might serve as a provisional intro- 
duction to the known career of man in the Nile region to 
the beginning of the period of the Second Glacial, which 
was long before the Heidelburg race appeared in Europe. 
This would place the origin of the human species in the 
Tertiary, an opinion contrary to that which has hitherto 
obtained. 



A PREHISTORIC PEDIGREE 179 

This conclusion is supported by other considerations. If 
the original human species arose in Africa, in the quarter 
where the earliest evidences are found, and later spread to 
western Asia, and the Neanderthals, like the Cro-Magnons, 
originally migrated thence, there must have been an enor- 
mous lapse of time before diverse types could have arisen 
from the first stock and increased to such numbers as to 
seek new regions and slowly penetrate thousands of miles 
of perilous wilderness to reach their final abode. Even if 
the Neanderthals came from northwestern Africa across 
the land bridges then existing, the conclusion here advanced 
is not materially disturbed. After knowledge of metals had 
reached the ^Egean area, a thousand years passed before it 
came to Britain and Scandinavia. It was a thousand years 
after the beginning of Roman civilization that the reaction 
upon the barbarians of the north was strong enough to 
incite a successful invasion. The factor of time thus be- 
comes a paramount factor of the problem. Furthermore, 
if this view of the remote origin of man be well founded 
it modifies or displaces another theory which has long been 
foremost in such speculations. 

PITHECANTHROPUS 

In 1891, near Trinil, Java, was found part of the skull 
of what has since been known as Pithecanthropus erectus 
(upright-standing ape-man). With it were unearthed two 
molar teeth and a left thigh bone. These remains, if all 
belong to the same individual, are parts of the only creature 
thus far discovered which had some characteristics of a 
pre-human species. Bones of other animals, including 
monkeys, found with the remains prove that all were depos- 
ited in the late Pliocene or early Pleistocene, when Java was 
joined with the Asiatic continent. The discovery of the so- 
called "missing link" aroused wide interest. The press of 
that day devoted no little space to the subject, and the 
discussion of it has continued to the present time. 

Taken in connection with the low human development of 



180 OUR WORLD 

the Heidelburg, Piltdown and Neanderthal species alone, 
Pithecanthropus seemed to have great significance. If it 
were a member of a pre-human species, the fact of 
evolution agrees with the theory; hence evolutionists were 
tempted to draw that conclusion in the absence of evi- 
dence of a greater age of the human species than was then 
known. During recent years, however, on more mature 
consideration of the Trinil skull itself, eminent authorities 
have inclined to displace the species from the ancestral 
human line and regard it as belonging to a branch of the 
original generalized stock from which the human and an- 
thropoid types have both come. This opinion is confirmed 
if the fact be established that man already existed as such 
during the epoch of the super-apes of Java. In that case, 
evidence of the direct line of human descent is yet to be 
discovered. 

A solitary example of the Trinil species, without inter- 
mediate types with progressively human characteristics, does 
not in any view establish a position in the line of human 
ancestry, however lowly the appearance and habit of species 
in that line. It only shows that at a remote period a race 
of apes existed with more distinctly human resemblances 
than have been possessed before or since by any other an- 
thropoids known. All this is quite obvious, but the impli- 
cations are important to the theory of human evolution. 

The so-called human characteristics seen in the simian 
types are chiefly the traits of incipient intelligence, possessed 
also in other degrees and other ways by many animals. 
Their peculiar evolution would not have been possible with- 
out them. Man, as a higher animal, has all these lower 
mental traits in combination as the basis of his higher fac- 
ulties. The same kind and degree of intelligence is natu- 
rally displayed in the same manner by the creatures that 
possess it. In its earliest phases, therefore, the quality of 
intelligence lowest in the human scale would also be shown 
by the apes, though modified by other characteristics, mainly 
physical, which predominate. The capacity of the Trinil 



A PREHISTORIC PEDIGREE 181 

skull is less than three-fourths of the brain capacity of the 
smallest specimen of the Neanderthal race yet found, though 
much greater than that of the chimpanzee. Despite its 
human resemblance in some particulars, the Trinil species 
was too remote from the human stock and too highly spe- 
cialized to be ancestral in the evolution of the human brain. 

THE ANTHROPOIDS 

If the process of divergence of the Trinil type was similar 
to that so often seen in organic history as to illustrate the 
principle, the original human (as distinguished from the 
immediate pre-human) stock was as distinct from the origi- 
nal anthropoid as the anthropoid stocks are different from 
one another. As the causes which produced the anthropoids 
throughout their evolution operated decisively at the time 
of the divergence, the longer the time afterward the greater 
were the differences and the more fixed the special types. 
The powers which have enabled the human species to ad- 
vance instead of being irretrievably moulded and fixed in 
type by circumstance have been due to the possession of 
a mental organ capable of surmounting natural obstacles that 
otherwise could not have been overcome. The disappear- 
ance of whole races of human beings is explained by their 
lack of brain, usually through physical deterioration, capable 
of standing the strain of conditions, while others were so 
constituted th?t they could and did or were not subjected 
to similar disadvantages. Apes, therefore, did not become 
human. A divergent branch from the primal source, the 
potential human line, became apes. 

This aspect of the question should be clearly understood 
in order to avoid a common misapprehension of the theory 
of organic evolution. Much of the opposition to the Dar- 
winian theory has been due to that misapprehension; and 
much of the discussion of the Trinil specimen has furthered 
it. Even many people who would otherwise accept the 
theory of biological origin and evolution refuse to recognize 
the ape as an ancestor. The reason may be sentiment or 



182 OUR WORLD 

prejudice, but it is none the less effective. To these it may 
be helpful to know that Pithecanthropus is nowise needful 
to the evolutionary origin of man. 

The question whether the anthropoids appeared before 
or after the distinctively human stock is purely speculative, 
as proofs bearing upon it are yet wanting. The type ap- 
parently originated in one or more abortive variations in the 
process of mental evolution before the ultimate line was 
definitely established. Since that line was strong enough 
in the beginning to control its evolution afterward, it is 
reasonable to suppose that throughout the early stages the 
nascent human type was distinct from species in which 
mental limitations were impassably fixed. Whatever may 
have been the resemblance during the first stages of both 
types, the superior power of the pre-human line would have 
reacted sooner on the physical development; hence at the 
time the higher anthropoids attained their climax, man, 
though still in a lowly human stage was nevertheless dis- 
tinctly human and was gradually adding to the volume of 
a brain already of necessity much greater than any anthro- 
poid could have had. That brain, moreover, had the power 
of yet greater growth, which the brain of the ape did not 
have. Thus considered, the history of the anthropoids 
becomes more significant. 

The record of the apes is very incomplete, but there is 
enough to mark the long term of their later evolution. The 
beginning has not been found. The remains of one of the 
forerunners of the great apes was exhumed in the desert 
near the Fayum, in Egypt. As that specimen was deposited 
in the Oligocene, the origin of the order must date earlier 
than the opening of the Tertiary. It resembled the gibbons, 
of which true arboreal types were in Europe early in the 
Miocene, and they continued there in various forms during 
the Pliocene. Other apes were also in Europe in both the 
Miocene and the Pliocene. In the Pliocene a generalized 
form related to the gibbon, the chimpanzee, the orang, and 
the gorilla lived among the Siwalik hills of Asia. It is 



A PREHISTORIC PEDIGREE 183 

agreed that none of these types can be regarded as ancestral 
to man. Yet the common descent from the remote original 
source of the pre-human line is undoubted. The anatomy 
of paleolithic man compels this conclusion. 

Much has been written concerning the process of man's 
structural evolution. That process is resolved by all author- 
ities into four principal factors: the erect attitude, the op- 
posable thumb, the power of speech and the growth of the 
brain. The latter must have been the cause of the others, 
though benefiting in turn by the effects. The earliest known 
apes walked more or less erect and were therefore dexterous 
in the use of their hands. Neither then nor later did they 
have the opposable thumb or the power of speech. The 
two upper grinders of the Trinil specimen more nearly 
resemble the form of the corresponding human teeth than 
do those of the gibbon, yet very clearly they do not confirm 
even in this detail the theory of the pre-human character 
of the animal. The thigh bone is so much like that of man 
that the creature walked erect and had full use of its arms 
and hands. The sensory areas of the brain — of touch, taste 
and vision — predominated. The central areas — of memory 
— were well developed, as with all the higher apes. The 
entire pre-frontal region was scanty, showing very slight 
ability to profit by experience. With such a rudimental 
mind, speech would not have been possible, nor would the 
probable form of the lower jaw have permitted. In seeking 
elsewhere for pre-human species the most promising geo- 
logic period is not in the Pleistocene of Pithecanthropus 
or even the late Pliocene. More probably, if the proofs 
ever come to light, they will be found in the lower Tertiary. 

THE PRE-HUMAN SPECIES 

Throughout biological history the phases of radical tran- 
sition are the most difficult to trace and therefore the least 
certainly known. They were necessarily the most rapid. 
The chief causes were changes in environment, which bore 
most heavily and swiftly upon many forms of life subjected 



184 OUR WORLD 

to them. Highly specialized types, which could not conform 
disappeared, while those more generalized and therefore with 
more plastic organisms readily changed along with the con- 
ditions. The comparative speed of the evolution greatly 
reduced the number of individuals affected and so dimin- 
ished the chances of their fossils being preserved and found. 
The pre-human species were the most adaptable and re- 
sponsive when conditions required, and their potential brain 
accelerated the process. Every succeeding change was has- 
tened accordingly when the circumstances raised no hin- 
drance. The human race no doubt began in the most favor- 
able region and was aided by a congenial environment. 
Measured by years, the advance was relatively rapid when 
all the conditions were propitious, as it ever since has been. 
When we consider the slowness with which superstitions 
die and sound ideas penetrate the mind of the multitude, 
even amid the enlightenment of the present age, there is 
no cause to marvel at the vast periods of time required 
by primitive human progress to reach the dawn of civili- 
zation. 



CHAPTER VII 
MIND AND THE AGGREGATE 

TRUE PSYCHOLOGY 

INTELLECTUAL progress is the gradual adjustment of 
mind to matter. It has therefore been precisely in the 
ratio of the advance in knowledge of nature. And this is 
so because of the physical character of the brain. The pri- 
mary function of the brain is to register sensations brought 
to it by the nervous system; and all sensations, at least in 
their origin, are produced by material means. All living 
tissues are more or less sensitive and thus respond to their 
environment. The processes of growth would otherwise be 
impossible. 

Despite the enormous and ever-multiplying literature of 
psychology, the known facts that underly the science are 
greatly disproportionate to the superstructure of theory ; and 
the most important principles are still in dispute. Even 
this situation shows a vast improvement over the former 
license of metaphysical speculation, which reveled in com- 
plete detachment from physical facts. The first great stage 
of a true mental science was achieved when psychology was 
brought within the definite boundaries of physiology. 

The brain being a physical development, the laws of its 
evolution are the same as those which govern all animal 
growth and adaptation. Physiological functions necessitate 
communication of the parts and more or less central con- 
trol of the combination. Each is dependent upon the others, 
and all are but different media of the forces, whatever they 
may be, that produce the varied phenomena of life. The 
human mind is the culmination of organic development, 
which had to pass through the successive stages of physical 
organization and aptitude to the point where consciousness 

185 



186 OUR WORLD 

became objective and the powers of perception began to rec- 
ognize the relation of cause and effect. And this has been 
through increase of function and the corresponding product 
of the means of exerting it. The origin and evolution of 
life are therefore coincident with the origin and evolution 
of mind; and the prime factors are wholly unknown. We 
are here brought through another avenue of approach to 
the problem of the constitution of matter and the cause of 
atomic and sub-atomic motion manifested in heat, light and 
electricity and the phenomena of chemical action. 

ORIGIN AND EVOLUTION 

The evolution of all forms of plant and animal life from 
one probable source and form very naturally suggests the 
idea that the origin itself was mechanistic. And that idea 
has of course been present from the beginning of philo- 
sophic thought ; but it possessed no tangible foundation until 
the modern demonstration of the origin of species and the 
development of organic chemistry. Given the suitable con- 
ditions of temperature, moisture and essential elements of 
matter, biochemical combination, very minute and in the sim- 
plest form, became inevitable. Such is the prevailing opinion 
of men of science at the present day, notwithstanding the 
absence of any positive evidence of spontaneous generation. 
However, a multitude of facts have been slowly accumu- 
lating for the structure of proof ; and the most important 
of these are the recent discoveries concerning the consti- 
tution of matter as the embodiment and vehicle of energy. 
Life is essentially a manifestation of energy, making use, 
so far as known, of the several forms with which science 
is familiar and acting through and upon familiar materials, 
though there are good grounds for suspecting the operation 
of another kind of energy, which has thus far eluded analy- 
sis, but which may be the dominating force in living things. 

The mystery of life has been the most prolific source of 
speculation and has naturally led to the most pernicious 
dogmas that have afflicted mankind, through their controlling 



MIND AND THE AGGREGATE 187 

influence upon thought and action. These dogmas range 
from the crude anarchy of chance to the centralized des- 
potism of divine predestination, none of which find counte- 
nance in the principles affirmed by science. While this is 
not the place for discussion of the great subject that for 
generations has exercised a legion of writers on theology 
and metaphysics, a few observations from a practical point 
of view will be pertinent and may aid in correcting the 
erroneous assumption in some quarters that science is sheer 
materialism, in its restricted sense, and the negation of a 
Creative Purpose in the phenomena of nature. 

If the adjustment of the waters and the atmosphere to 
the conditions which have made the earth an abode of life 
were to be regarded as the result of chance, the odds, within 
the definite law of probabilities, would be immeasurably 
against it. The factors of the problem are so many and 
so perfectly proportioned that only a mind reckless of all 
considerations of rational possibility can conceive that mere 
chance wrought these wonders out of chaos. But there can 
be no chaos in the primary meaning of the word. Even 
in the most heterogeneous mass, the elements composing it 
exist intact with all their properties, ever ready to separate 
or recombine in other forms according to the forces exerted 
upon them. So, when the chemical elements that enter into 
organic combination are multiplied into the other factors and 
this result into the marvelous attributes of the elements 
themselves, the existence of life and mind through blind 
chance is so remote that no one acquainted with the terms 
of the proposition would hazard a guess at such a solution. 
Yet, leaving out of thought the alternative Cause as beyond 
the reach of finite faculties, there is such ample scope for 
the operation of natural forces upon the diversity and in- 
stability of matter that the results are variable and contin- 
gent. This plasticity of circumstance is the medium of 
chance. And it is the inter-relation of all phases of the 
conditions that renders true science and philosophy syn- 
thetic. 



188 OUR WORLD 

For twenty-three centuries, from Empedocles to Darwin, 
the idea of evolution was germinating. Within fifty years 
from the publication of the Origin of Species the principle 
had won the unanimous acceptance of the scientific world. 
Those five decades mark the greatest and most salutary revo- 
lution in the history of thought ; and this consequence would 
not have been possible but for the rapid progress of scien- 
tific methods, which brought about a new attitude of mind 
toward nature — the disposition to ascertain facts and to 
accept their logical import regardless of doctrines and pre- 
conceptions. 24 

That there is still some misapprehension of the true char- 
acter and meaning of organic evolution is due to confound- 
ing the principle with criticism of Darwin's effort to explain 
it by what he termed natural and sexual selection, or, as 
put by Spencer, the survival of the fittest. This rationale 
was soon challenged, and the debate is not yet ended. The 
disputants, however, have all been evolutionists. Their dif- 
ferences have not been over the seriated features of evolu- 
tion, but over the precise means by which the processes 
of heredity and variation are carried on. The total result 
has been to stimulate investigation and amass proofs of 
the development of one order of organisms from another 
throughout the entire history of life on the earth. 

A fact established is consistent with every other fact bear- 
ing effective relation to it. Truth, like light, radiates in all 
directions. When, therefore, the vast array of evidence 
from the ever increasing collection of fossils, as well as 
from the classification and geographical distribution of plants 
and animals, past and present, demonstrated evolution by 
adaptation, it was inevitable that every other aspect of life 
would be in harmony with that principle. 

If land vertebrates originated from amphibians having 
four legs, it was entirely consistent that their successors, 
except those which have lost some or all through reverse 
adaptation, should have four limbs, particularly as four have 
been enough for every form that ever existed. With these 



MIND AND THE AGGREGATE 189 

four limbs and the spine, it was likewise consistent that 
all the species should be essentially similar in physical struc- 
ture, the variations being those required by the different 
functions exercised. These facts have been shown so abun- 
dantly and in such minute detail that they need only be 
alluded to here. Nor need more than a mere reference be 
made to the blood tests which reveal the distant kinship 
of different species of animals descended from the same 
stock ; nor to the remarkable results of variation produced 
by experiment and by the domestication of both plant and 
animals. Even more decisive, if possible, are the rudimental 
vestiges of organs and parts plainly reminiscent of func- 
tions active during remote stages of evolution, but long 
fallen into disuse. These are present in all higher animals 
and notably in the human species, which have no fewer 
than 1 80. Yet, as conclusive as these several lines of demon- 
stration have been, the most striking phenomena are those 
displayed by the embryo of every animal form large enough 
to be studied in detail. 

Like natural selection, embryology has been the subject 
of much controversy and with the same result: the proc- 
esses are in debate, but the principle of evolution is con- 
firmed in the most graphic manner. The most significant 
illustration is the human foetus. 

THE HUMAN EMBRYO 

All animals, including the human species, begin in a single 
cell containing a nucleus. Starting in comparative simplicity, 
they develop into greater complexity. The human ovum 
or egg is about 125th of an inch in diameter; while the 
male or sperm cell that enters it and starts its development 
is very much smaller. This minute combination of living 
female and male matter holds all the characteristics of the 
future man or woman. During the first three months of 
foetal development, all the great transformations take place. 
It is then that the human foetus strikingly resembles that 
of the lower animals. 



190 OUR WORLD 

The fertilized ovum divides into two cells, these again 
divide, and this process of division continues, the cells defi- 
nitely arranging themselves into tissues and organs. At 
about the third week the body cavities which enclose the 
organs begin to appear. The foetus is then in the vermian 
stage. Having acquired a true body cavity, it becomes 
higher in construction than ccelenterate animals. In the 
second week the wormlike embryo begins to have a seg- 
mented body. In the following week four grooves appear 
in the neck representing the gill slits of fishes, while the 
heart also has the two-chambered form seen in fishes. Gills 
however, are not actually developed, but the structure shows 
a line of descent from ancestors among the fishes and am- 
phibians. By the sixth week the gill slits have disappeared 
and the foetus has passed to the lunged state. The heart 
then has the three chambers seen in the amphibia ; gradu- 
ally this becomes the four-chambered organ of the mam- 
mals, though it begins to beat at the two-chambered stage. 
The lungs are not used until birth, the placenta serving the 
purpose of respiration. 25 

THE CHEMISTRY OF LIFE 

In Huxley's phrase, protoplasm is the physical basis of 
life. Despite the enormous amount of investigation and 
speculation devoted to the subject since Huxley's time, the 
general fact thus characterized has received little further 
explanation. The mystery has baffled chemical analysis 
and the microscope. 

In this great field of the unknown lies the future of the 
most important research and discovery; and the prospect 
is the more encouraging because all the known elements 
of the problem are amenable to the methods of physical 
science. A glance at these features is needful in any expo- 
sition of the evolution of the brain, which in its physical 
character is similar to all other parts of the organism. 

As water has been the most important agency in the 
transformation of the earth's surface and the liberation of 



MIND AND THE AGGREGATE 191 

the chemical elements fused together in the igneous rocks, so 
it has been the chief vehicle of the organic chemistry by 
which life originated and has been maintained. Water is 
thus the basis of protoplasm, giving it the more or less 
fluid or colloidal character that enables it to utilize the chem- 
ical elements and compounds supplied to it. Inasmuch as 
water does not react with most biological substances, it pro- 
motes biochemical stability. Equally important is its dielec- 
tric constant, mentioned in a former connection, which ren- 
ders it the best conductor of electric ionization in solution 
without disassociation of its own molecules. Its great sur- 
face tension furthers the capillary attraction so vital to plant 
growth. There can be no doubt that, however life origi- 
nated, water was the medium. 

At least twenty-nine of the chemical elements have been 
found in different living organisms ; most of them, however, 
when present are in very minute proportions. The principal 
elements are hydrogen, oxygen, nitrogen and carbon. So 
important to life is carbon that organic chemistry is essen- 
tially the chemistry of its compounds, of which there are 
known to be over 100,000, probably exceeding those formed 
by all the other elements, while there are thousands of com- 
pounds of carbon, hydrogen and oxygen, and hundreds of 
carbon and hydrogen. 26 The vast majority of organic sub- 
stances contain no other elements than these four. Phos- 
phorous, sulphur, potassium, calcium, magnesium, iron and 
perhaps silicon are also present in all living organisms, 
except some of the most primitive bacteria, and are there- 
fore regarded as essential to existing life. Besides these, 
chlorine, sodium, iodine and fluorine are commonly found 
as constituents. 

It will thus be seen that the materials of life comprise 
most of the chemical elements of frequent occurrence in 
the rocks, the waters and the atmosphere. The metallic 
elements being charged positively and the non-metallic nega- 
tively, their action and reaction, through electrolytic ioniza- 
tion, are no doubt closely related to the activities of proto- 



192 OUR WORLD 

plasm ; for they always take place in the presence of oxygen 
and with energy that comes directly or indirectly from the 
sun. Not only have no substances been found in organic 
matter except those familiar to chemistry, but no form of 
energy has been discovered in living things that is not 
derived from the inorganic world. 27 Yet back of all this 
are the mysterious powers of the heredity-germ which, from 
the beginning of life on the earth, has accumulated its pecu- 
liar powers over the definite organism it gives rise to, as 
well as perpetuating itself in its successors, with all those 
potentialities which have permitted the diversity of species 
since life originated in its first minute and simple forms. 

The physical agency that causes or furthers the interaction 
or coordination of the parts of an organism, so far as known, 
is catalysis, in familiar use by chemists and on a large 
scale in some industries. A catalyzer hastens or retards 
chemical changes without being itself permanently affected. 
The mechanism of this action is unknown. The theory is 
that the phenomena are caused by the alternate attachment 
and detachment of the catalyzer to and from the substance 
upon which it acts. It is well known, however, that the 
enzymes are the principal organic catalyzers, different kinds 
acting upon different substances with different results ; and 
all are produced by the organism itself. Their action is in 
a high degree specific and is therefore instrumental in ac- 
complishing a great variety of effects necessary to the many 
organic functions, from the instant the system obtains air 
and sustenance to the final formation of tissues and the 
removal of waste. 

The agents in general are styled chemical messengers, as 
they are discharged into the circulation of the blood and thus 
carried to the regions where they become effective. The 
simplest of them are by-products of single chemical reac- 
tions, such as carbon dioxide eliminated by the cells through 
breathing. This product, because of its acidic properties, 
is one of the chief regulators of respiration. The enzymes 
are far more complex. Their development appears to be 



MIND AND THE AGGREGATE 193 

concurrent with the evolution of the organism as a part of 
its functional mechanism. They are supposed to reside in 
the nuclei of the cells, for the activity of the cell itself 
seems to depend upon them. The active agents of the 
external excretions are always in the nature of a ferment or 
enzyme. When an organism is invaded, elsewhere than 
inside the alimentary canal, by active foreign proteins, such 
as bacterial infection, the venom of snakes and insects and 
some vegetable poisons, they act as enzymes, causing chem- 
ical messengers, called anti-bodies, to arise for the protec- 
tion of the tissues involved. The neutralizing anti-bodies 
are commonly known as anti-toxins. When the intruding 
protein (antigens) is not of an active order, the business 
of the anti-bodies is merely to remove the invader, without 
producing any degree of immunity from another similar 
attack. The function of curative medicines is, in like man- 
ner, to further the natural chemical processes of the body 
in counteracting the abnormal conditions caused by disease. 
The ductless glands are laboratories for the production of 
specific substances that pass directly into the blood stream 
with a stimulating, modifying or inhibiting effect upon other 
organs. Most of the vital and characteristic operations of 
the physical system, including the brain, are traceable to such 
activities. From such phenomena it may be fairly deduced 
that the interactions, of which these instances are typical, 
are the physico-chemical agencies which have been the alter- 
nating cause and effect of the very processes of evolution 
itself. 

In the course of evolution the quality of its products has 
never been slighted. So ready is the response of nature to 
the requirements of life that whatever the functions to be 
served, the appropriate material, in perfect form and finish, 
is normally forthcoming to effectuate it. Each of the chem- 
ical life elements has peculiar properties adapted to those 
functions and freely enters into organic compounds for that 
definite service. When we consider the innumerable spe- 
cies of plants and animals that in the long cycle of evolution 



194 OUR WORLD 

have flourished and disappeared, we may form some idea 
of the inexhaustible resources of the elements that form 
organic compounds; for it is evident that the variety of 
substances composing them must have been fully as great 
as the number of species, if not many times greater. The 
plastic attributes of the inorganic elements that so wonder- 
fully fit them to organic processes prompts the inference 
that life arose in response to universal laws of matter when 
the physical environment evoked their operation. All the 
facts now known point to the conclusion that organic powers 
and functions have evolved simultaneously with the forms 
they produced, proceeding from the simplest to the most 
complex. If this complexity, which finds its highest devel- 
opment in the human brain, has been the normal product 
of physical evolution, the volume of life automatically in- 
creasing with favorable conditions, the origin was probably 
due to the cooperation of peculiar conditions and the in- 
herent properties of matter. Such is the gist of the argu- 
ment of those who prefer to think that all the phenomena 
of life, like those of the inorganic world, are the result of 
law and not of supernatural intervention. 

THE UNITS OF GROWTH AND FUNCTION 

Cytology, the science of the cells, has made no radical 
advance since the discovery of the inheritance of definite 
characters in the primary cell (Mendelism) and the estab- 
lishment of the theory that the chromatin (so called from 
its peculiar capacity for taking stain, which renders it dis- 
tinguishable under the lens) constitutes the heredity-germ. 
Naturally all the resources of microscopy and chemical 
analysis have been directed unceasingly to the solution of 
the mystery; but all have been futile. Analytical chem- 
istry can deal only with dead protoplasm after the subtle 
and elusive forces of life have ceased to act, while the 
infinitestimal minuteness of all structures lies far beyond 
the power of the microscope to reveal. "In recent years," 
says Eddington, speaking of gravitation, "great progress 



MIND AND THE AGGREGATE 195 

has been made in knowledge of the excessively minute ; but 
until we can appreciate the details of structure down to 
the quadrillionth or quintillionth of a centimeter, the most 
sublime of all the forces of nature remains outside the pur- 
view of the theories of physics. " If the secret of gravita- 
tion be thus baffling, not less so are the problems of life, 
heredity and variation, and probably for the same reasons. 
Despite the enormous and unabated volume of speculation 
and controversy which these subjects have occasioned, we 
are no nearer to positive knowledge of the ultimate cause 
of these wonders than in Darwin's time, except as discus- 
sion has eliminated one theory after another from the babel 
of argument. "While we know," says Osborn, "the hered- 
ity chromatin to be the physical basis of inheritance and the 
presiding genius of all phases of development, we cannot 
form the slightest conception of the mode in which the 
chromatin speck of the germ cell controls the destinies of 
Sequoia gigantea and lays down all the laws of its being for 
its long life period of five thousand years. We are equally 
ignorant as to how the chromatin responds to these actions, 
reactions and interactions of the body cells of the life envi- 
ronment and of the physical environment so as to call forth 
a new adaptive character, unless it be through some infi- 
nitely complex system of chemical messengers and other 
catalytic agencies." 28 

New cells come into existence only by division of pre- 
existing cells. In a comparatively few cases the cell propa- 
gates by giving off a bud, which soon matures into a new 
cell ; otherwise cell-reproduction is always through the equal 
division of an old cell into two new ones — the source of all 
growth and replacement in the higher plants and animals. 
Inasmuch as this process, known as mitosis, is observable 
in its larger aspects, the successive phases are well under- 
stood. Yet this knowledge lends no precise aid in solving 
the vital problem. We observe an infant grow into a 
youth, and the youth into a man; we know more or less 
of the physical agencies that enter into this development and 



196 OUR WORLD 

witness the physical changes they produce; but the main- 
spring of it all is undisclosed. As the man is but an aggre- 
gation of cells and their products, the problem remains 
where it was. However, as with evolution, what is known 
of the physical processes warrants the supposition that the 
unknown factors are of the same order, that is to say, normal 
and universal properties of matter under suitable conditions. 

The unit of microscopic measurements is the micron, 
which is i/iooo of a millimetre. Rutherford estimates that 
the diameter of the sphere of action of an atom is i/io,- 
000,000 of a millimetre. The most compact type of chro- 
matin is that of the sperm-nucleus of the sea-urchin, esti- 
mated at about 1/100,000,000 of a cubic millimetre. As 
the electron is about 1/1800 of the mass of the hydrogen 
atom, the lightest known to science, the mass of the electron 
would be only 1/18,000,000 of a micron. Thus within the 
limits of the cell nucleus would be ample room for a mul- 
titude of mutually acting, reacting and interacting particles 
of matter, which constitute the source of life and direct 
the energies of the heredity-germ. 

The difficulties in finding any concrete bases for specula- 
tion, owing to the ultra-microscopic nature of the under- 
lying cell activities, are illustrated by the uncertainty as to 
whether any bacteria are the typical cell with its protoplasm 
and distinct nuclear chromatin. Bacteriologists (the word 
was not introduced until 1884) differ radically on all points, 
though they agree as to the presence of granules of the 
chromatin type, leaving as an open question whether or not 
there is a structurally distinct nucleus. In like manner it is 
unsettled whether protoplasm and chromatin originally ap- 
peared one before the other or both together. 

No questions have ever been more suited to controversy 
than those relating to the origin of life and its fundamental 
processes, and the debate will doubtless proceed until some 
more tangible basis is found than has thus far been dis- 
covered. However these questions may be regarded, there 
is no doubt that the peculiar development of the brain cells 



MIND AND THE AGGREGATE 197 

and the organ they constitute has been an evolution extend- 
ing over the whole duration of life on the earth, and that 
the brain, with its attendant nervous system, has physically 
corresponded to the organism it accompanied and has been 
proportional in quality to the character of the activities it 
has regulated. 

THE BRAIN A PHYSICAL EVOLUTION 

A living thing composed of but a single cell, though of 
an animal nature, needs no brain or nervous system. The 
mere protoplasm of Protozoa is endowed with such sensi- 
bility to its environment and such perfect conductivity of 
effect that it is presumed to be the medium by which the 
nervous system of the higher animal organisms receives 
and transmits sensations. Why and how this is so is un- 
known. Sensations travel through a normal nervous system 
at a rate not exceeding 300 feet a second; but what it is 
that travels and how it travels — that is, the nature of the 
impulse — is still a mystery ; the effects of sensations are well 
understood, but not what a sensation is. The mechanism 
and the impulse are manifestly of the same character in all 
animal organisms ; the differences are of degree and not of 
kind. Thus the more complex the organism and the higher 
its functions, the more elaborate the system of communica- 
tion and coordination and therefore the more intricate the 
constitution of the brain as the organ by which the inter- 
actions are regulated. All this has been demonstrated by 
anatomy and is in perfect accord with physiological theory. 

The differentiation of the cells of necessity kept pace with 
the evolution of the Metazoa. In other words, the higher 
the organism the more complex the mechanism of its ac- 
tivities, the more various the materials entering into its 
structure, and therefore the greater the diversity of the cells 
to meet these manifold requirements. The nervous system 
and the brain were the organic response to the call of need. 
The evolution and adaptation of the cells to perform these 
functions are part of the mystery of life itself ; and not less 



198 OUR WORLD 

profound than the secret of vitality is that of the capacity 
of the cell, as the organic unit, to perform its precise office 
wherever placed, while cooperating with the system of which 
it is a minute member, and obeying all the behests of the 
heredity-germ to which it owes its existence. 

The intellectual functions of the brain are due to con- 
sciousness, the paramount attribute of mind that marks all 
higher animals, and in man forms the basis of all his 
vaunted faculties; yet what consciousness is, in the last 
analysis, is as inscrutable as what life is. The futile efforts 
to account for the phenomenon have produced most of the 
jargon of superstition and metaphysics. Nevertheless, some 
conclusions from known facts are warranted. Although the 
exact relation between the conscious mind and the brain is 
unknown, the mind (with all that the word implies) is ab- 
solutely dependent upon the activities of the brain as a 
physical organ ; and proceeding a step further, the nervous 
system and the brain comprise the mechanism by which the 
external stimulations are transformed into organic behavior. 
The degrees of effective consciousness range from the sim- 
plest voluntary actions in lowly organisms to the highest 
flights of human genius. From these facts it is clear that 
consciousness itself is as much an evolution as the physical 
agencies that make it possible. And all the lesser degrees are 
present in every normal living person. There is, therefore, 
no true science of the mind apart from physiological 
psychology ; yet knowledge of the physiology of the nervous 
system is very scanty. Relatively little is known concerning 
the nervous action of the brain. At the present time, even 
physiological psychology is little more than a series of 
neurological facts on the one hand and of facts of con- 
sciousness on the other. 29 

The functions of the various organs are, for the most part, 
automatic. We are unconscious of their action, unless they 
are involved in some abnormal condition such as injury or 
disease, that causes disturbance of the tissues and their 
communicating nerves. The progress of modern physiology 



MIND AND THE AGGREGATE 199 

has been largely due to the discovery of the physico-chem- 
ical offices of the glands of the system, of which the most 
expert were formerly ignorant; and the subject is still far 
from exhausted. The fundamental processes of life are 
automatic ; and it is because they are so highly ramified, so 
nicely adjusted, and so obscure withal, that surgery as a 
science is so far in advance of medicine. Diagnosis is too 
often a misguided guess, while the knife exposes the condi- 
tion. The circulation of the blood was not generally recog- 
nized until toward the close of the seventeenth century ; and 
the complicated properties of the blood are still an increas- 
ing source of discovery in the field of biology and the treat- 
ment of disease. 

During antiquity and when the Greeks formulated their 
philosophies the seat of the mind was variously located in the 
liver, the kidneys, the heart and elsewhere, rather than in 
the brain. Plato thought the marrow of the bones the like- 
liest place, to the derision of Aristotle, who nevertheless sup- 
posed that the purpose of the brain is to regulate the tem- 
perature of the blood ; and the influence of his teachings was 
very great until the progress of science began to displace the 
notions which had so long prevailed. During the centuries 
when theology and metaphysics were most industrious in de- 
fining the nature and destiny of man, primarily because of 
his intellect, the functions of the brain were mostly un- 
known. In fact it was not until the middle of the nineteenth 
century that the foundation was laid for a scientific 
psychology. 

Physical coordination was necessarily long before con- 
scious action was even elementary. This is shown by the 
autonomic nervous system, which lies outside of the spinal 
column. It is connected, of course, with the cerebro-spinal 
nervous system, but is relatively independent, controlling 
respiration, circulation, digestion and glandular action, 
which are automatic. The system, in various forms, was 
present in all animal organisms above the very lowest be- 
fore the Vertebrates appeared. Obviously the spinal cord 



200 OUR WORLD 

and its branches were not less important in the evolution of 
the Vertebrates than the spine itself. Yet physical organiza- 
tion and power reached their highest development far in 
advance of mentality. In the gigantic reptiles, in which brain 
evolution was in a primitive stage, the coordination of the 
limbs was evidently reinforced by a sort of relay station — a 
sac of spinal fluid or nerve substance in the sacrum, the 
region of the vertebrae sustaining the monstrous tail and 
huge hind legs. 

If specimens of the brain at the different stages of its 
evolution were available they would add but little to the 
knowledge derived from the known forms and activities of 
extinct animals and the shapes and capacities of their brain- 
cases. Moreover, among existing orders the progressive 
stages clearly confirm the theory of mental evolution. The 
facts are so well established that the general process is rep- 
resented by the chief characteristics of this development in 
the brains of the higher mammals. 

The disparity between the brain-power of the highest 
reptiles and the earliest mammals was not greater than be- 
tween that of the archaic mammals and their remote 
descendants. Different habits, varied adaptation of tooth 
structure to the foods consumed and increase in size as well 
as flexibility and power of movement required and pro- 
duced corresponding brain development; and the rapidity 
of mammalian evolution as compared with that of other 
types was due to this mental improvement in many direc- 
tions. As a large proportion of the mammals, then and 
later, were carnivorous, the most physically fit had the ad- 
vantage, and the inferior succumbed. Likewise, the herbi- 
vorous orders developed powers of alertness, speed and 
agility as their best defense against rapacious foes. The 
gradual development of these physical characteristics was 
necessarily attended, as a part of the process, by correspond- 
ing changes in the nervous system and the brain. Thus the 
brains of succeeding species of the progressive orders in- 
creased in size and functions. Many series of skulls of dif- 



MIND AND THE AGGREGATE 201 

ferent types very graphically exhibit the extent and char- 
acter of this development. 

THE MECHANISM OF THE BRAIN AND NERVOUS SYSTEM 

Throughout the entire range of the phenomena of sensa- 
tion, from the lowest forms of animal life to the highest, 
the mechanism is of the same character and operates by the 
same forces. The evolution of the human brain is traced 
through many successive stages precisely parallel with the 
evolution of animal form and organization. In all Verte- 
brates, from fishes to man, the nerve masses originate in 
the outer part of the blastoderm, the living portion of the 
ovum from which the embryo and all its membranes are de- 
rived. At first three and subsequently five consecutive 
brain-vesicles are formed by expansion at the first section 
of the spinal cord. From these vesicles the greater divisions 
of the brain, with all their complicated incidents, are de- 
veloped. The course and character of the development 
necessarily differ with the nature of the organism, but in 
man and the apes the analogy is very close. 

The first vesicle becomes the cerebrum; the second, the 
optic thalamus ; the third, the corpora quadrigemina ; the 
fourth, the cerebellum; and the fifth the medulla oblongata. 
The cerebrum steadily overlaps and finally covers the cere- 
bellum, which develops slowly, the lateral lobes at the ex- 
pense of the middle one. As the cerebrum increases in vol- 
ume the surface begins to fold, producing convolutions and 
fissures, which give the position of the different orders in 
the organic scale. In man they reach their highest evolution 
in number and complexity. In its earliest stages, the develop- 
ment of the brain, like that of the organism, is similar in all 
Vertebrates. In the succeeding stages extensive modifica- 
tions take place; but even here the brains of all mammals, 
bear resemblance in structure, the departures from the 
common form corresponding to the grade of intelligence 
possessed by the animal. The division of the brain into two 
hemispheres is characteristic of the organ wherever it ex- 



202 OUR WORLD 

ists, and of course becomes more distinct with the higher 
development of its functions. The separation, however, is 
not complete. The two parts are united by a broad band of 
fibres called the corpus callosum ; yet the fissure extends the 
entire length of the cord and divides it in halves. 

From the base of the human brain twelve pairs of cranial 
nerves extend. Some carry only sensory fibres, some only 
motor, and some carry both. As the name implies, the 
sensory nerves relate to the consciousness ; the motor, to the 
various organic functions that are more or less automatic. 
From the spinal cord thirty-one pairs extend, each nerve 
being attached to the cord by two roots. One is composed 
chiefly of sensory fibres from cell bodies of the spinal 
ganglia ; the other, of motor fibres the cell bodies of which 
lie within the gray matter of the spinal cord. The two unite 
after leaving the cord and form a complete spinal nerve. 
These pairs of nerves are distributed along the entire length 
of the spine, and their innumerable extensions and ramifi- 
cations complete the cerebro-spinal nervous system. 

The nerve cells, called neurones, are the units of the 
nervous mechanism, which is the most complicated thing in 
nature. Their importance in the physical system may be in- 
ferred from their number, estimated at some ten thousand 
million in every adult person, every neurone being in itself 
a complex organ capable of many connections. They are 
present throughout the brain and all the tissues. The gen- 
eral scheme of this immensely complicated system may be 
gathered from the principal features. 

The neurones are of three classes. The sensory or affer- 
ent bring stimuli to the brain and spinal cord; the motor 
or eflferent carry stimuli from these centers to the muscles ; 
and the associative or central, comprising the elaborate 
mechanism — the greater part of the brain — by which the 
sensory and motor neurones are connected, thus controlling 
and coodinating the functions of the organism. Those which 
cross from one-half of the brain or cord to the other are 
termed commissural. "Even if we knew," says Thorndike, 



MIND AND THE AGGREGATE 203 

"the exact arrangement of each neurone in a man's brain, 
it would take a model as large at St. Paul's Cathedral to 
make them visible to the naked eye." 30 

The distinguishable peculiarity of the neurones is that the 
enlarged portion, containing the cell nucleus and possessing 
the ordinary properties of other cells, is only a part of the 
unit which includes threadlike prolongations and branches 
that terminate in a number of minute strands like the frayed 
ends of a string. The fine-spun terminals of the sensory 
neurones serve the purpose of gathering the sensations con- 
veyed to the other parts. The cell body operates in most 
cases to reinforce and regulate the impulses brought from 
the extremities and passed on in transit to the brain. The 
motor neurones perform the converse function of carrying 
the governing impulses from the brain to the muscles. With 
all this maze of nervous apparatus, intimately connected and 
perfectly adjusted, in normal conditions, is an almost equally 
wonderful conjunction with the physiological processes by 
which the organism is sustained and activated ; and all this 
without regard to the nature of the organism, the differ- 
ences being in detail and not in essential character or method. 

The white appearance of the greater part of the brain 
texture, the cord and the nerves is due to the medullated 
sheath of the nerve fibres. The gray matter is the true 
nerve substance and constitutes the cortex or outer layer of 
the brain, certain ganglia within the brain and the core of 
the spinal cord. The cortex is of course protected by mem- 
branes from contact with the skull. The physiological char- 
acter of the human brain and its kinship with the mental 
mechanism of all other animals is evident without detailed 
description of its parts. Some further reference, however, 
to the cortex, which contains all the centers of the mental 
processes, is necessary. 

The most remarkable and inexplicable characteristic of 
the cortex is the apparent absence of any of the conscious 
functions from one of the hemispheres. Usually the left 
half is the active one ; yet to all appearances the two are 



204 OUR WORLD 

perfectly matched. The dispositions of gray matter in them 
correspond fissure for fissure, lobe for lobe, and convolution 
for convolution; and these also agree in every particular 
except for some differences in size and shape, with the brain 
of the chimpanzee. With other higher animals the parts of 
the brain are perfectly analogous, exhibiting the same gen- 
eral conformation and arrangement, composed of the same 
materials and operating in the same way. The differences 
in form are only such as are produced by the differences in 
the functions served. The mysterious attributes of the hu- 
man brain exist alike in the brains of all other animals. 
These facts are not to be ignored in any consideration of the 
human intellect. To disregard them is to proceed upon as- 
sumptions for which there is no scientific warrant. 

The neurones of the cortex are arranged in strata, each 
stratum containing those of a characteristic type. The thick- 
est stratum holds neurones of a pyramidal form, pointing 
toward the surface. They are associated with the higher 
mental processes; and the degree of intelligence, in both 
man and animals, depends upon the size and number of these 
cells and their appendages. The number in the brain of the 
human foetus increases until the third or fourth month, 
when the limit for the individual is reached. After that 
time the only changes are in their structure and in the 
length and complexity of their branches. The ultimate qual- 
ity and calibre of every brain are therefore fixed before 
birth and are governed by the precise character of the 
physical structure. The cause of many psychological 
phenomena was only surmised until it was fully demon- 
strated by exact investigation of many types of brain, hu- 
man and other. 

The sensorial, language and associational centres are 
normally located in the left hemisphere. Cases have been 
known where disease has practically destroyed the gray 
matter of the right hemisphere, together with the corpus 
callosum, which connects it with the left, without directly 
affecting the faculties, but producing paralysis of the right 



MIND AND THE AGGREGATE 205 

side of the body. From such evidence it is manifest that the 
right hemisphere, while without the purely mental functions 
exercised by the left, nevertheless contains motor areas 
which control extensive muscular action. On the other hand, 
lesions of various parts of the left cortex, caused by injury 
or disease, always involve corresponding loss or impair- 
ment of function. These consequences have enabled 
psychology to map the active cortical hemisphere with cer- 
tainty as to the senses, language and the principal faculties. 
This index, however, is not to be confounded with the 
fanciful notions of phrenology, which have no tangible 
basis whatever. 

The functions of very considerable areas of the cortex 
both in the pre- frontal regions and elsewhere, adjacent to 
known centres, have not been determined. Inasmuch as all 
the higher intellectual faculties are associational, these parts 
are supposed to be the seat of the complex adjustments and 
correlations essential to those operations. At all events, 
there is no reason to doubt that the intellect, in its highest 
powers, is as distinctly physical in its action as any other 
feature of mentality. 31 

THE SOURCE OF THE SENSES 

All the sense organs have been developed from the in- 
tegument and have nerves connected with them. This is the 
common bond which unites the entire kingdom down to 
Protozoa, which have no differentiated sense organs, but 
receive sensations over all parts of the surface. Thus the 
sense of touch in the most primitive. Organs for the percep- 
tion of light were next in the order of evolution. The eyes 
of all vertebrates have essentially the same system of in- 
tegument and nerve elements. The evolution of the eye and 
the visual sense is readily traced from a simple pigment spot 
to the highly complicated eye structure and vision of the 
Vertebrates and man. As the eye was produced by the in- 
tegument in response to vibrations of the ether, so the sense 
and organ of hearing were produced in response to the vi- 



206 OUR WORLD 

brations of the air. Very little is yet known concerning the 
physiology of smell and taste. Both functions have arisen in 
answer to the needs of the animal organism through the 
action of material forces. The associational system by which 
all the impressions received by the brain are adjusted is 
equally obscure. 

Such are the salient facts of psychology regarded as the 
climax of physiological evolution ; and such is the basis of 
the vast mass of speculation and dogma to which the nature 
of the human mind has given rise. It may be confidently 
assumed that the solution of many of the mysteries that now 
baffle the understanding is more promising in the field of 
physiology than in the domain of philosophic disputation. 32 

THE EVOLUTION OF SOCIETY 

About the same proportion of mere hypothesis to the body 
of observed facts in the science of psychology obtains in 
sociology, the science of society. The temptation to specu- 
lation and the motives for dogma are about the same in 
both. As the mind gives character to the individual, so the 
average of its units gives character to society. If the mind 
is the reflex of material conditions and human activities are 
circumscribed by them, the individual and society should 
conform to principles perfectly adjusted to them. This con- 
clusion would seem to be the logical and necessary result 
of the nature of man so far as science has been able to de- 
termine it from the physical elements of the world in which 
he lives and of which he is a part. This conclusion involves 
certain limitations and great difficulties of application, espe- 
cially in minds unwilling or unable to accept the physical 
evidence. 

It is clearly as much the function of science to disclose 
the elements of human conduct as it is to explore the ma- 
terial environment and reveal the constitution and nature 
of things. The ultimate purpose of science that justifies its 
development in the past and its promise of future service is 
the benefit that accurate knowledge must bring to the course 



MIND AND THE AGGREGATE 207 

of civilization. It is not proposed here to venture upon any 
philosophic discussion, but the survey we have now made 
of the physical conditions of our world and ourselves war- 
rant some general observations upon the material aspects 
of the greater human problems. 

In contemplating the rise of the human species with the 
potentialities of mind which have made possible the human 
intellect at its best, and regarded solely upon the evidence 
as a physical evolution, one is prompted to inquire whether 
any feature of human history reveals anything more than 
a natural part of the process. The most prominent fact in 
human evolution is the relation of the quality of intellectual 
development to the accumulation of experience. There can 
be little question that in mere capacity the average brain of 
the Cro-Magnon some 25,000 years before the beginning of 
the historic period was fully equal to that of the present 
time. The skeletons and skulls of those races indicate that 
in physique they were not inferior to any living race, and 
that the brain as a physical organ had attained its character- 
istic form and functions. This is the most fundamental fact 
in considering the nature and extent of human progress. It 
is in harmony with sound psychology and reconciles the facts 
of history with the principle of evolution. 

The slow progress from the period of sheer savagery, 
when the race first began to use weapons and utensils rudely 
fashioned by accidental means, to the establishment of the 
original centers of civilization was due to the gradual 
changes in the structure of the brain corresponding with the 
functions arising from increased experience. And it is sig- 
nificant that the process was similar to that which marked all 
other forms of organic evolution. For example, the Neander- 
thal type does not appear to have changed much in body or 
brain during the many centuries of its dominance in Europe. 
It was evidently displaced by a higher type originating else- 
where and making its way by reason of mental superiority. 
How such new types arise is a matter of controversy ; but it 
is generally conceded that, in some cases at least, they do 



208 OUR WORLD 

occur by mutations. The history of ancient civilization, like 
that of modern times, shows that highly gifted minds ap- 
peared at intervals and exerted a vast influence upon their 
surroundings. Such influences brought new experiences and 
improved or altered social conditions, which of course re- 
acted upon adjacent communities and succeeding times. 

This factor of racial progress during the early phases of 
civilization is especially prominent because of the relatively 
long periods they covered and the restriction of the record, 
in the main, to such public events as wars, revolutions and 
royal succession. The historical methods that now prevail 
are distinctly modern; and the application of them to the 
revision of ancient history by utilizing the economic and so- 
cial elements that formed the background of the more con- 
spicuous public events emblazoned in the chronicles is one of 
the most striking indications of the pervasive scientific 
spirit in which all the conditions of human activity have 
come to be regarded. 

The results of this recasting and amplification of ancient 
and medieval history according to the standards of actual 
experience in modern times and in the light of scientific 
principles have been to demonstrate the evolution of thought 
as reflected in manners, customs and institutions. In perfect 
analogy to physical evolution throughout geologic time, this 
progress has been fitful and sporadic. When conditions fav- 
ored progress an advance occurred — now here, now there, 
but always adding to the total of experience and thus to the 
momentum which in the long run has been superior to the 
immediate obstacles. No historical narrative better exhibits 
the principles of social evolution than Gibbon's Decline and 
Fall of the Roman Empire. Although written in the last 
quarter of the eighteenth century, when modern science was 
in its initial stage, the work is entitled to rank as the great- 
est single contribution to descriptive sociology. Here may be 
found the most remarkable series of events and conditions 
in human history, disclosing phenomena of all the principal 
types, thus affording a basis of comparative anatomy, so to 



MIND AND THE AGGREGATE 209 

speak, by which to study the evolution of the social organism 
and to aid in diagnosing its existing ills. 

The most powerful and constant influence in human his- 
tory has been the general belief, in one form or another, 
that supernatural agencies operate in the affairs of man- 
kind. This influence has been effective in proportion to the 
degree of popular ignorance of natural conditions. The fact 
that from aboriginal and prehistoric times the great mass of 
human beings have sought explanation of the unknown in 
the supernatural has been accepted as proof of the prin- 
ciple. An appeal to elementary psychology should refute 
this conclusion. 

It was inevitable that when the mind arrived at the stage 
of conscious intelligence it should ask the questions Whence 
and Whither ? Every normal child does so, very early in the 
course of its mental development. Any race of human be- 
ings that failed to do so would have been abnormal and men- 
tally defective, whatever the stage of its evolution. It was 
equally natural and inevitable that, in the absence of knowl- 
edge, the conception of supernatural power as the explana- 
tion of mystery should arise. The idea, therefore, proves 
nothing; and the prevalence of it has gradually diminished 
as the frontiers of the unexplained have receded. 

The development of society from the tribal form to mod- 
ern nationality is as clearly an evolution as the race itself. 
That the process is far from complete renders the subject 
of profound interest as the crowning problem of scientific 
thought. The greatest and most deviously persistent ob- 
struction to an ideal form has proceeded, directly or indi- 
rectly, from the fundamental vice — adherence to ideas, mostly 
theological, that took root in the superstitions arising from 
ignorance of the causes of natural phenomena. Religious 
wars and forcible religious propaganda and repression as a 
factor in human affairs have ceased, except in some rela- 
tively small regions which have not as yet felt the full force 
of the conditions that prevail in more enlightened nations. 
But the retarding effects of such ideas are still very prev- 



210 OUR WORLD 

alent indirectly. Cults and creeds based on any form of 
superstition or dogma inevitably seek power and either 
aggressively or insidiously affect political institutions. These 
influences are rife and everywhere more or less powerful. 

Since the American and French revolutions, the idea of 
the divine right of royal rulers has been steadily waning. 
Perhaps the most important effect of Napoleon's career has 
been to hasten its expulsion. In the Germanic empires the 
principle was sedulously fostered and thus formed the basis 
of the unquestioning loyalty and obedience of the masses to 
the behests of imperial policy. Rulers who assert them- 
selves to be divine representatives necessarily assume that 
their opinions are conclusive, their prerogatives supreme, 
and their territorial expansion justified whatever the means. 
Such rulers would have been quite helpless without some 
delegation of their prerogatives and powers ; hence arose the 
nobility and privileged classes, who were likewise bene- 
ficiaries of the popular illusion. 

Victor Hugo's observation at the close of his description 
of the battle of Waterloo, that Napoleon failed because he 
was not in harmony with the nineteenth century, applies to 
the teutonic attack upon the principles of civil liberty. The 
Prussian Kultur was not in accord with the twentieth cen- 
tury — with the course of evolution which has brought man- 
kind to its present status. It is enough to remark that at no 
former period would it have been possible for the more ad- 
vanced nations to combine for the assurance of the prin- 
ciples that underly their civilization and that must eventually 
develop social, economic and governmental conditions giv- 
ing proper scope to the powers and rights of individuals as 
the units of all institutions. 

With the complete suppression of the archaic forces that 
caused the conflict, the world will enter upon a new sociolog- 
ical era as clearly defined as any of the stages of organic 
evolution. Yet it would be rash prophecy that ventured to 
specify the results of the new conditions that will have 
arisen. Those conditions will be plastic and embrace a com- 



MIND AND THE AGGREGATE 211 

plexity of elements that have never been operative in many 
nations where centralized government and inveterate cus- 
toms and habits of mind have determined and limited their 
action. Even in pre-existing republics the exigencies of war 
compelled the exercise of powers that would have been re- 
sentfully denied in normal times. The situation thus created 
cannot long endure. The return to conditions of peace has 
already brought with it new ideas and purposes engendered 
by the extraordinary experiences through which civilization 
had passed even in those countries where the effects of the 
conflict are only indirect. Efforts to realize those objects will 
provoke political activity in which forces long latent will 
assert themselves. It is probable, therefore, that in the dis- 
tant future of civilization the twentieth century will take 
rank in the scale of social evolution with the Tertiary in 
the evolution of life. 

These considerations supply the practical reasons why 
education should invariably and systematically include in- 
struction in the fundamental sciences as the basis of all 
other teaching after children have learned to read and 
write. Opinions and beliefs formed in ignorance of the 
natural causes through which the world has been brought 
to its present physical condition, of the nature of man and 
mind and the true functions of political institutions, in- 
evitably react and form the chief obstruction to progressive 
ideas. 

The great events of history, in all their variety, have been 
in the main but episodes in the evolution of social conditions. 
Yet this evolution as reflected in the science of government 
and administration has not been commensurate with the ef- 
forts expended to establish true principles. The obstacles 
have been too various and too deeply rooted in custom and 
power long exerted to yield readily to ideals which have not 
been in agreement. Nevertheless, the general and funda- 
mental principle of popular sovereignty has made such wide 
and steady progress that the phase of absolutism, however 
disguised or diluted, is approaching its end. 



212 OUR WORLD 

All this is the result of materialism in its highest sense, 
which is not to be confounded with the narrow one sought 
to be imposed upon it by those who assert supernatural 
agencies in human affairs. In this sense materialism signi- 
fies natural results from natural causes, excluding any other 
explanation of phenomena. The action of natural forces de- 
pends solely upon the physical conditions in which they oper- 
ate. Heat, for example, when controlled, supplies comfort 
and service ; unchecked, it destroys. Throughout the whole 
realm of life and mind this familiar principle holds true. 

Materialism, then, in its true sense, is knowledge of 
natural forces and intelligent control of them. Weapons of 
war in the hands of the foes of progress must ever be met 
in kind and overcome by superior force. But the gravest 
dangers are in stealthy reaction, and the ranks of reaction 
are always recruited from the uninformed and seek justi- 
fication in oppressive conditions. The greatest measure of 
civilization will not be achieved until justice, the morals of 
society, is established among nations and among all the ele- 
ments of every nation. Such is the prospect of ultimate 
evolution. Such is the promise of science. 



THE END 



NOTES 

Most of the following notes are offered as a guide to 
readers who may desire to pursue further some of the more 
important topics presented by the text. In a work of this 
kind references are unnecessary. All statements of fact 
may be taken as justified by standard works in the several 
divisions of science to which the facts relate. 

i. In 1916 a star was discovered somewhat nearer # than Alpha 
Centauri, to which it appears to have some relation, possibly that of a 
third member of a system long supposed to be binary. Proxima 
Centauri is dark red and very faint, being of about the nth magni- 
tude. 

2. The Evolution of the Stars and the Formation of the Earth, by 
W. W. Campbell, a series of lectures before the National Academy 
of Sciences, published in The Scientific Monthly, September-Decem- 
ber, 1915. An Introduction to Astronomy, by F. R. Moulton, will 
supply a more detailed view of the general subject. The Binary 
Stars, by R. I. Aitken, is a recent and valuable contribution to the 
subject of stellar evolution. 

3. LowelFs principal books, Mars and Its Canals, Mars as an 
Abode of Life and The Evolution of Worlds will repay attentive 
perusal. They are models of "popular science." 

4. The physical arguments that life exists on Venus and does not 
exist on Mars are set forth in The Destinies of the Stars, by Arrhe- 
nius. This volume contains many suggestive considerations as to 
various cosmic problems. 

5. What We Know About Comets, by W. W. Campbell, in The 
Scientific Monthly, December, 1916, gives an authoritative account of 
these objects; and The Story of the Comets, by G. F. Chambers, the 
history of their visitations. 

6. Meteorites: Their Structure, Composition and Terrestrial Re- 
lations, by O. C. Farrington. 

7. "The difference," says Sir Joseph Thompson, "between the 
laws of gravitation of Einstein and Newton comes only in special 
cases. The real interest of Einstein's theory lies not so much in his 
results as in the method by which he gets them. If his theory is 
right it makes us take an entirely new view of gravitation. _ The 
weak point in the theory is the great difficulty of expressing it. It 

213 



214 OUR WORLD 

would seem that no one can understand the new law of gravitation 
without a thorough knowledge of invariants and of the calculus of 
variations. One other point of physical interest arises. Light is 
deflected in passing near large bodies of matter. This involves 
alterations in the electric and magnetic fields outside of matter — 
forces at present unknown, though some idea of their nature may be 
got from the results of the eclipse expedition." 

All science has hitherto been based on the Euclidean system of 
geometry. That system assumes that all measurements are from the 
rigid data by which plain areas and cubic content are calculated. 
Newton's law of gravitation is based on that geometry. The theory 
of Relativity depends upon a system of geometry that calls for a 
fourth dimension — the "time-space manifold/' This is calculated 
only by super-mathematics; and it imports a difference in results so 
minute as to be ascertainable only for astronomic distances. It 
therefore does not enter into consideration as to any of the ordinary 
subjects of physical science. 

The theory has yet a hard road to travel before it can gain general 
acceptance by men of science; but it will doubtless aid in a better 
understanding of the ultimate forces of the universe. A very intelli- 
gible exposition of it is set forth in a lecture of Edwin B. Wilson, 
Space, Time and Gravitation, published in The Scientific Monthly, 
March, 1920. 

8. The Sun, by C. G. Abbott. The details of the organization of 
the Solar System are given in Moulton's Introduction to Astronomy. 

9. The Planetesimal Hypothesis is fully presented in The Origin 
of the Earth, by T. C. Chamberlin. 

10. Elements of Geology, by W. H. Norton, gives in a clear and 
concise form a good knowledge of both branches of the science. 

11. An Introduction to Historical Geology, by W. J. Miller, is an 
excellent work suited to the general reader. 

12. The Old Red Sandstone, by Hugh Miller, should be read. 
This classic is valuable not only as showing the pleasure and profit 
of geological studies in the field, but the tenacity with which early 
naturalists clung to the idea of special creations. 

13. In relation to the Cretaceous, Huxley's lecture, On a Piece of 
Chalk, in his Lectures and Lay Sermons, should be read. 

14. A New Era of Chemistry, by H. C. Jones. 

15. Chemical Discovery and Invention in the Twentieth Century, 
by Sir William A. Tilden. 

16. The Electron, by R. A. Millikan. 

17. The Nature of Matter and Electricity, by Comstock and Tro- 
land ; Outlines of Theoretical Chemistry, by F. H. Getman. 

18. Paleontological Evidences of the Antiquity of Disease, by 
R. L. Moodie, The Scientific Monthly, September, 1918. 



NOTES 215 

19. The reptilian origin of the mammals is still disputed. The 
argument in support of the amphibian source is given in Chapter 
XVII of The Causes and Course of Evolution, by J. M. Macfarlane. 

20. Evolution and Animal Life, by Jordan and Kellogg; Organic 
Evolution, by R. S. Lull ; The Age of Mammals, by H. F. Osborn. 

21. A History of the Warfare of Science with Theology, by 
Andrew D. White. 

22. Men of the Old Stone Age, by H. F. Osborn. 

23. The Origins of Civilization, by J. H. Breasted, a series of lec- 
tures before the National Academy of Science, published in The 
Scientific Monthly, October, 1919-February, 1920. 

24. The best and most authoritative account of the idea of Evolu- 
tion is From the Greeks to Darwin, by H. F. Osborn. Darwin's in- 
fluence in all the main departments of science since his time is well 
displayed in Darwin and Modern Science and Fifty Years of Darwin- 
ism, each a symposium by eminent scientists, published in 1909 in 
commemoration of the centenary of Darwin's birth. 

25. Text Book of Geology, by Pirsson and Schuchert, page 963. 

26. Outlines of Organic Chemistry, by E. J. Moore. 

27. Creative Evolution, by H. Bergson, illustrates the futility of 
attempting the advance physical science by philosophic disquisition. 

28. The Origin and Evolution of Life, by H. F. Osborn; The 
Causes and Course of Evolution^ by J. M. Macfarlane; The Evolu- 
tion of the Earth and Its Inhabitants, by Professors Burrell, Schu- 
chert, Woodruff, Lull and Huntington, of Yale University. 

29. Psychology, by B. B. Breese. 

30. The Elements of Psychology, by E. L. Thorndike. The illus- 
trations in this volume are a most valuable feature. 

31. Brain and Personality and What Is Physical Life?, by W. H. 
Thomson, are valuable to the general reader. The facts presented 
are culled from the author's extensive professional experience. Strict 
logic, . however, leads to conclusions quite different from those 
reached by him. 

32. The relation of man to other animals, in physical and mental 
evolution, is fully demonstrated in The Human Species, by L. Hopf. 
The value of Huxley's classic, Man's Place in Nature, has never been 
impaired. 



